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Lecture notes, cheat sheets
Microbiology. Lecture notes: briefly, the most important
Directory / Lecture notes, cheat sheets Table of contents
LECTURE No. 1. Introduction to microbiology 1. Subject and tasks of microbiology Microbiology is a science, the subject of which is microscopic creatures called microorganisms, their biological characteristics, systematics, ecology, relationships with other organisms. Microorganisms are the most ancient form of organization of life on Earth. In terms of quantity, they represent the most significant and most diverse part of the organisms inhabiting the biosphere. Microorganisms include: 1) bacteria; 2) viruses; 3) mushrooms; 4) protozoa; 5) microalgae. A common feature of microorganisms is microscopic dimensions; they differ in structure, origin, physiology. Bacteria are unicellular microorganisms of plant origin, devoid of chlorophyll and without a nucleus. Mushrooms are unicellular and multicellular microorganisms of plant origin, devoid of chlorophyll, but having features of an animal cell, eukaryotes. Viruses are unique microorganisms that do not have a cellular structural organization. The main sections of microbiology: general, technical, agricultural, veterinary, medical, sanitary. General microbiology studies the most general patterns inherent in each group of the listed microorganisms: structure, metabolism, genetics, ecology, etc. The main task of technical microbiology is the development of biotechnology for the synthesis of biologically active substances by microorganisms: proteins, enzymes, vitamins, alcohols, organic substances, antibiotics, etc. Agricultural microbiology deals with the study of microorganisms that participate in the cycle of substances, are used to prepare fertilizers, cause plant diseases, etc. Veterinary microbiology studies the pathogens of animal diseases, develops methods for their biological diagnosis, specific prophylaxis and etiotropic treatment aimed at the destruction of pathogenic microbes in the body of a sick animal. The subject of study of medical microbiology is pathogenic (pathogenic) and opportunistic microorganisms for humans, as well as the development of methods for microbiological diagnostics, specific prevention and etiotropic treatment of infectious diseases caused by them. A branch of medical microbiology is immunology, which studies the specific mechanisms of protection of human and animal organisms from pathogens. The subject of study of sanitary microbiology is the sanitary and microbiological state of environmental objects and food products, the development of sanitary standards. 2. Systematics and nomenclature of microorganisms The main taxonomic unit of bacterial taxonomy is the species. A species is an evolutionarily established set of individuals that has a single genotype, which under standard conditions is manifested by similar morphological, physiological, biochemical and other features. The species is not the final unit of taxonomy. Within the species, variants of microorganisms are distinguished, differing in individual characteristics. So, they distinguish: 1) serovars (by antigenic structure); 2) chemovars (according to sensitivity to chemicals); 3) fagovars (by sensitivity to phages); 4) fermenters; 5) bacteriocinovars; 6) bacteriocinogenovars. Bacteriocins are substances produced by bacteria that have a detrimental effect on other bacteria. According to the type of bacteriocin produced, bacteriocinovars are distinguished, and according to sensitivity, bacteriocinogenovars are distinguished. For species identification of bacteria, it is necessary to know the following properties: 1) morphological (shape and structure of a bacterial cell); 2) tinctorial (the ability to stain with various dyes); 3) cultural (nature of growth on a nutrient medium); 4) biochemical (the ability to utilize various substrates); 5) antigenic. Species related by genetic relationship are combined into genera, genera - into families, families - into orders. The higher taxonomic categories are classes, divisions, subkingdoms and kingdoms. According to modern systematics, pathogenic microorganisms belong to the kingdom of prokaryotes, pathogenic protozoa and fungi - to the kingdom of eukaryotes, viruses are combined into a separate kingdom - Vira. All prokaryotes that have a single type of cell organization are combined into one department - Bacteria. However, some of their groups differ in structural and physiological features. On this basis, there are: 1) actually bacteria; 2) actinomycetes; 3) spirochetes; 4) rickettsia; 5) chlamydia; 6) mycoplasmas. Currently, a number of taxonomic systems are used for the taxonomy of microorganisms. 1. Numerical taxonomy. Recognizes the equivalence of all signs. To use it, it is necessary to have information about many dozens of features. The species affiliation is established by the number of matching characters. 2. Serotaxonomy. It studies bacterial antigens using reactions with immune sera. Most often used in medical bacteriology. The disadvantage is that bacteria do not always contain a species-specific antigen. 3. Chemotaxonomy. Physico-chemical methods are used to study the lipid, amino acid composition of a microbial cell and certain of its components. 4. Genetic systematics. Based on the ability of bacteria with homologous DNA to transform, transduce and conjugate, on the analysis of extrachromosomal factors of heredity - plasmids, transposons, phages. The totality of the basic biological properties of bacteria can only be determined in a pure culture - these are bacteria of the same species grown on a nutrient medium. 3. Nutrient media and methods for isolating pure cultures For the cultivation of bacteria, nutrient media are used, to which a number of requirements are imposed. 1. Nutrition. The bacteria must contain all the necessary nutrients. 2. Isotonic. Bacteria must contain a set of salts to maintain osmotic pressure, a certain concentration of sodium chloride. 3. Optimal pH (acidity) of the medium. The acidity of the environment ensures the functioning of bacterial enzymes; for most bacteria is 7,2-7,6. 4. Optimum electronic potential, indicating the content of dissolved oxygen in the medium. It should be high for aerobes and low for anaerobes. 5. Transparency (so that bacterial growth can be seen, especially for liquid media). 6. Sterility (so that there are no other bacteria). Classification of culture media 1. By origin: 1) natural (milk, gelatin, potatoes, etc.); 2) artificial - media prepared from specially prepared natural components (peptone, aminopeptide, yeast extract, etc.); 3) synthetic - media of known composition, prepared from chemically pure inorganic and organic compounds (salts, amino acids, carbohydrates, etc.). 2. By composition: 1) simple - meat-peptone agar, meat-peptone broth, Hottinger agar, etc.; 2) complex - these are simple with the addition of an additional nutrient component (blood, chocolate agar): sugar broth, bile broth, whey agar, yolk-salt agar, Kitt-Tarozzi medium, Wilson-Blair medium, etc. 3. By consistency: 1) solid (contain 3-5% agar-agar); 2) semi-liquid (0,15-0,7% agar-agar); 3) liquid (do not contain agar-agar). 4. By appointment: 1) general purpose - for the cultivation of most bacteria (meat-peptone agar, meat-peptone broth, blood agar); 2) special purpose: a) elective - media on which bacteria of only one species (genus) grow, and the genus of others is suppressed (alkaline broth, 1% peptone water, yolk-salt agar, casein-charcoal agar, etc.); b) differential diagnostic - media on which the growth of some types of bacteria differs from the growth of other species in one way or another, more often biochemical (Endo, Levin, Gis, Ploskirev, etc.); c) enrichment environments - environments in which reproduction and accumulation of pathogenic bacteria of any kind or species occurs, i.e. enrichment of the material under study (selenite broth). To obtain a pure culture, it is necessary to master the methods for isolating pure cultures. Methods for isolating pure cultures. 1. Mechanical separation on the surface of a dense nutrient medium (stroke method by firing a loop, method of dilutions in agar, distribution over the surface of a solid nutrient medium with a spatula, Drygalsky method). 2. Use of elective nutrient media. 3. Creation of conditions favorable for the development of one species (genus) of bacteria (enrichment environment). A pure culture is obtained in the form of colonies - this is an isolated accumulation of bacteria visible to the naked eye on a solid nutrient medium, which, as a rule, is the progeny of one cell. LECTURE No. 2. Morphology and ultrastructure of bacteria 1. Structural features of a bacterial cell. Main organelles and their functions Differences between bacteria and other cells 1. Bacteria are prokaryotes, that is, they do not have a separate nucleus. 2. The cell wall of bacteria contains a special peptidoglycan - murein. 3. There is no Golgi apparatus, endoplasmic reticulum, mitochondria in a bacterial cell. 4. The role of mitochondria is performed by mesosomes - invaginations of the cytoplasmic membrane. 5. There are many ribosomes in a bacterial cell. 6. Bacteria may have special movement organelles - flagella. 7. The sizes of bacteria range from 0,3-0,5 to 5-10 microns. According to the shape of the cells, bacteria are divided into cocci, rods and convoluted. In a bacterial cell, there are: 1) main organelles: a) nucleoid; b) cytoplasm; c) ribosomes; d) cytoplasmic membrane; e) cell wall; 2) additional organelles: a) disputes; b) capsules; c) villi; d) flagella. The cytoplasm is a complex colloidal system consisting of water (75%), mineral compounds, proteins, RNA and DNA, which are part of the nucleoid organelles, ribosomes, mesosomes, and inclusions. Nucleoid is a nuclear substance dispersed in the cytoplasm of a cell. It does not have a nuclear membrane or nucleoli. It contains DNA, represented by a double-stranded helix. Usually closed in a ring and attached to the cytoplasmic membrane. Contains about 60 million base pairs. It is pure DNA, it contains no histone proteins. Their protective function is performed by methylated nitrogenous bases. The nucleoid encodes the basic genetic information, i.e. the cell genome. Along with the nucleoid, the cytoplasm can contain autonomous circular DNA molecules with a lower molecular weight - plasmids. They also encode hereditary information, but it is not vital for a bacterial cell. Ribosomes are ribonucleoprotein particles 20 nm in size, consisting of two subunits - 30 S and 50 S. Ribosomes are responsible for protein synthesis. Before protein synthesis begins, these subunits combine into one - 70 S. Unlike eukaryotic cells, bacterial ribosomes are not combined into an endoplasmic reticulum. Mesosomes are derivatives of the cytoplasmic membrane. Mesosomes can be in the form of concentric membranes, vesicles, tubules, in the form of a loop. The mesosomes are associated with the nucleoid. They are involved in cell division and spore formation. Inclusions are metabolic products of microorganisms that are located in their cytoplasm and are used as reserve nutrients. These include inclusions of glycogen, starch, sulfur, polyphosphate (volutin), etc. 2. The structure of the cell wall and cytoplasmic membrane The cell wall is an elastic rigid formation with a thickness of 150-200 angstroms. Performs the following functions: 1) protective, the implementation of phagocytosis; 2) regulation of osmotic pressure; 3) receptor; 4) takes part in the nutritional processes of cell division; 5) antigenic (determined by the production of endotoxin - the main somatic antigen of bacteria); 6) stabilizes the shape and size of bacteria; 7) provides a system of communications with the external environment; 8) is indirectly involved in the regulation of cell growth and division. The cell wall is not visible with conventional staining methods, but if the cell is placed in a hypertonic solution (during the plasmolysis experiment), it becomes visible. The cell wall closely adjoins the cytoplasmic membrane in gram-positive bacteria, in gram-negative bacteria the cell wall is separated from the cytoplasmic membrane by the periplasmic space. The cell wall has two layers: 1) outer - plastic; 2) internal - rigid, consisting of murein. Depending on the content of murein in the cell wall, Gram-positive and Gram-negative bacteria are distinguished (in relation to Gram stain). In Gram-positive bacteria, the murein layer makes up 80% of the mass of the cell wall. According to Gram, they are colored blue. In gram-positive bacteria, the murein layer makes up 20% of the mass of the cell wall; according to Gram, they are stained red. In gram-positive bacteria, the outer layer of the cell wall contains lipoproteins, glycoproteins, teichoic acids; they lack a lipopolysaccharide layer. The cell wall looks amorphous, it is not structured. Therefore, when the murein framework is destroyed, bacteria completely lose their cell wall (become protoplasts), and are not capable of reproduction. In gram-negative bacteria, the outer plastic layer is clearly defined, contains lipoproteins, a lipopolysaccharide layer consisting of lipid A (endotoxin) and polysaccharide (O-antigen). When gram-negative bacteria are destroyed, spheroplasts are formed - bacteria with a partially preserved cell wall that are not capable of reproduction. The cytoplasmic membrane is adjacent to the cell wall. It has selective permeability, takes part in the transport of nutrients, excretion of exotoxins, energy metabolism of the cell, is an osmotic barrier, participates in the regulation of growth and division, DNA replication, and is a ribosome stabilizer. It has the usual structure: two layers of phospholipids (25-40%) and proteins. According to their function, membrane proteins are divided into: 1) structural; 2) permiases - proteins of transport systems; 3) enzymes - enzymes. The lipid composition of membranes is not constant. It may vary depending on the cultivation conditions and the age of the culture. Different types of bacteria differ from each other in the lipid composition of their membranes. 3. Additional bacterial organelles Villi (pili, fimbriae) are thin protein outgrowths on the surface of the cell wall. Functionally they are different. There are komon-drank and sex-drank. Komon pili are responsible for the adhesion of bacteria to the surface of host cells. They are characteristic of Gram-positive bacteria. Sex pili provide contact between male and female bacterial cells during the conjugation process. Through them, genetic information is exchanged from the donor to the recipient. The donor - a male cell - possesses a sex-drank. The female cell - the recipient - does not have a sex drink. The sex pili protein is encoded by the F-plasmid genes. Flagella are organelles of movement. There are motile bacteria. These are special protein outgrowths on the surface of a bacterial cell containing a protein - flagelin. The number and arrangement of flagella may vary. Distinguish: 1) monotrichous (have one flagellum); 2) lophotrichous (have a bundle of flagella at one end of the cell); 3) amphitrichous (have one flagellum at each end); 4) peritrichous (have several flagella located around the perimeter). The motility of bacteria is judged by considering living microorganisms, or indirectly by the nature of growth in Peshkov's medium (semi-liquid agar). Non-motile bacteria grow strictly according to the injection, and mobile ones give diffuse growth. Capsules are an additional surface shell. They are formed when a microorganism enters a macroorganism. The function of the capsule is protection against phagocytosis and antibodies. There are macro- and microcapsules. The macrocapsule can be identified using special staining techniques, combining positive and negative staining techniques. Microcapsule - thickening of the upper layers of the cell wall. It can only be detected with electron microscopy. Microcapsules are characteristic of virulent bacteria. Bacteria include: 1) true capsular bacteria (genus Klebsiella) - retain capsule formation even when growing on nutrient media, and not only in the macroorganism; 2) pseudocapsular - form a capsule only when it enters the macroorganism. Capsules can be polysaccharide and protein. They play the role of an antigen, they can be a virulence factor. Spores are special forms of existence of some bacteria under adverse environmental conditions. Sporulation is inherent in Gram-positive bacteria. Unlike vegetative forms, spores are more resistant to chemical and thermal factors. Most often, spores form bacteria of the genus Bacillus and Clostridium. The process of sporulation consists in thickening of all cell membranes. They are impregnated with calcium dipicalinate salts, become dense, the cell loses water, and all its plastic processes slow down. When the spore gets into favorable conditions, it germinates into a vegetative form. Gram-negative bacteria also have the ability to survive in unfavorable conditions in the form of non-culturable forms. At the same time, there is no typical sporulation, but metabolic processes in such cells are slowed down, it is impossible to immediately grow on a nutrient medium. But when they enter the macroorganism, they turn into their original forms. LECTURE No. 3. Physiology of bacteria 1. Growth and reproduction of bacteria Growth of bacteria - an increase in the size of a bacterial cell without increasing the number of individuals in the population. Reproduction of bacteria is a process that ensures an increase in the number of individuals in a population. Bacteria are characterized by a high rate of reproduction. Growth always precedes reproduction. Bacteria reproduce by transverse binary fission, in which two identical daughter cells are formed from one mother cell. The process of bacterial cell division begins with the replication of chromosomal DNA. At the point of attachment of the chromosome to the cytoplasmic membrane (replicator point), an initiator protein acts, which causes the chromosome ring to break, and then its threads are despiralized. The filaments unwind and the second filament attaches to the cytoplasmic membrane at the pro-replicator point, which is diametrically opposed to the replicator point. Due to DNA polymerases, an exact copy of it is completed along the template of each strand. Doubling of genetic material is a signal for doubling the number of organelles. In septal mesosomes, a septum is being built, dividing the cell in half. Double-stranded DNA spiralizes, twists into a ring at the point of attachment to the cytoplasmic membrane. This is a signal for the divergence of cells along the septum. Two daughter individuals are formed. On dense nutrient media, bacteria form clusters of cells - colonies, different in size, shape, surface, color, etc. On liquid media, bacterial growth is characterized by the formation of a film on the surface of the nutrient medium, uniform turbidity or sediment. Reproduction of bacteria is determined by the time of generation. This is the period during which cell division takes place. The duration of generation depends on the type of bacteria, age, composition of the nutrient medium, temperature, etc. Phases of reproduction of a bacterial cell on a liquid nutrient medium: 1) initial stationary phase; the number of bacteria that got into the nutrient medium and is in it; 2) lag phase (rest phase); duration - 3-4 hours, bacteria adapt to the nutrient medium, active cell growth begins, but there is no active reproduction yet; at this time, the amount of protein, RNA increases; 3) phase of logarithmic multiplication; the processes of cell reproduction in the population are actively going on, reproduction prevails over death; 4) maximum stationary phase; bacteria reach the maximum concentration, i.e., the maximum number of viable individuals in the population; the number of dead bacteria is equal to the number of formed; there is no further increase in the number of individuals; 5) accelerated death phase; the processes of death prevail over the process of reproduction, since nutrient substrates in the environment are depleted. Accumulate toxic products, metabolic products. This phase can be avoided by using the flow culture method: metabolic products are constantly removed from the nutrient medium and nutrients are replenished. 2. Feeding bacteria Nutrition is understood as the processes of entry and removal of nutrients into and out of the cell. Nutrition primarily ensures the reproduction and metabolism of the cell. Among the necessary nutrients, organogens are distinguished - these are eight chemical elements, the concentration of which in a bacterial cell exceeds 10-4 mol. These include carbon, oxygen, hydrogen, nitrogen, phosphorus, potassium, magnesium, calcium. In addition to organogens, trace elements are needed. They provide enzyme activity. These are zinc, manganese, molybdenum, cobalt, copper, nickel, tungsten, sodium, chlorine. Bacteria have a variety of sources for obtaining nutrients. Depending on the source of carbon production, bacteria are divided into: 1) autotrophs (use inorganic substances - CO2); 2) heterotrophs; 3) metatrophs (use organic matter of inanimate nature); 4) paratrophs (use organic substances of wildlife). Nutritional processes must provide the energy needs of the bacterial cell. According to energy sources, microorganisms are divided into: 1) phototrophs (able to use solar energy); 2) chemotrophs (receive energy through redox reactions); 3) chemolithotrophs (use inorganic compounds); 4) chemoorganotrophs (use organic matter). Bacterial growth factors are vitamins, amino acids, purine and pyrimidine bases, the presence of which accelerates growth. Bacteria include: 1) prototrophs (they are able to synthesize the necessary substances from low-organized ones themselves); 2) auxotrophs (they are mutants of prototrophs that have lost genes; they are responsible for the synthesis of certain substances - vitamins, amino acids, therefore they need these substances in finished form). Microorganisms assimilate nutrients in the form of small molecules; therefore, proteins, polysaccharides, and other biopolymers can serve as food sources only after they have been broken down by exoenzymes into simpler compounds. Metabolites and ions enter the microbial cell in various ways. Ways of entry of metabolites and ions into the microbial cell. 1. Passive transport (without energy costs): 1) simple diffusion; 2) facilitated diffusion (along the concentration gradient, with the help of carrier proteins). 2. Active transport (with the expenditure of energy, against the concentration gradient; in this case, the substrate interacts with the carrier protein on the surface of the cytoplasmic membrane). There are modified variants of active transport - the transfer of chemical groups. Phosphorylated enzymes act as carrier proteins, so the substrate is transferred in a phosphorylated form. This transfer of a chemical group is called a translocation. 3. Metabolism of a bacterial cell Features of metabolism in bacteria: 1) the variety of substrates used; 2) intensity of metabolic processes; 3) the orientation of all metabolic processes to ensure reproduction processes; 4) the predominance of decay processes over synthesis processes; 5) the presence of exo- and endoenzymes of metabolism. There are two types of metabolism in the process of metabolism: 1) plastic (constructive): a) anabolism (with energy costs); b) catabolism (with the release of energy); 2) energy metabolism (occurs in the respiratory mesosomes): a) breathing b) fermentation. Depending on the acceptor of protons and electrons among bacteria, aerobes, facultative anaerobes and obligate anaerobes are distinguished. For aerobes, the acceptor is oxygen. Facultative anaerobes in oxygen conditions use the process of respiration, in anoxic conditions - fermentation. For obligate anaerobes, only fermentation is characteristic; under oxygen conditions, the death of the microorganism occurs due to the formation of peroxides, and cell poisoning occurs. In the microbial cell, enzymes are biological catalysts. According to the structure, they distinguish: 1) simple enzymes (proteins); 2) complex; consist of protein (active center) and non-protein parts; required for enzyme activation. There are also: 1) constitutive enzymes (they are constantly synthesized regardless of the presence of a substrate); 2) inducible enzymes (synthesized only in the presence of a substrate). The set of enzymes in a cell is strictly individual for the species. The ability of a microorganism to utilize substrates through its set of enzymes determines its biochemical properties. According to the place of action, there are: 1) exoenzymes (act outside the cell; take part in the process of disintegration of large molecules that cannot penetrate inside the bacterial cell; characteristic of gram-positive bacteria); 2) endoenzymes (act in the cell itself, provide the synthesis and breakdown of various substances). Depending on the chemical reactions catalyzed, all enzymes are divided into six classes: 1) oxidoreductases (catalyze redox reactions between two substrates); 2) transferases (carry out intermolecular transfer of chemical groups); 3) hydrolases (perform hydrolytic cleavage of intramolecular bonds); 4) lyases (attach chemical groups at two bonds, and also carry out reverse reactions); 5) isomerases (carry out isomerization processes, provide internal conversion with the formation of various isomers); 6) ligases, or synthetases (connect two molecules, resulting in the splitting of pyrophosphate bonds in the ATP molecule). 4. Types of plastic exchange The main types of plastic exchange are: 1) protein; 2) carbohydrate; 3) lipid; 4) nucleic. Protein metabolism is characterized by catabolism and anabolism. In the process of catabolism, bacteria decompose proteins under the action of proteases with the formation of peptides. Amino acids are formed from peptides by the action of peptidases. The breakdown of proteins under aerobic conditions is called smoldering, and under anaerobic conditions, decay. As a result of the breakdown of amino acids, the cell receives ammonium ions necessary for the formation of its own amino acids. Bacterial cells are able to synthesize all 20 amino acids. Leading among them are alanine, glutamine, asparagine. They are involved in the processes of transamination and transamination. In protein metabolism, synthesis processes predominate over decay, while energy consumption occurs. In carbohydrate metabolism in bacteria, catabolism prevails over anabolism. Complex carbohydrates of the external environment can be broken down only by those bacteria that secrete enzymes - polysaccharidases. Polysaccharides are broken down to disaccharides, which, under the action of oligosaccharidases, decompose to monosaccharides, and only glucose can enter the cell. Part of it goes to the synthesis of its own polysaccharides in the cell, the other part undergoes further cleavage, which can go in two ways: along the path of anaerobic decomposition of carbohydrates - fermentation (glycolysis) and under aerobic conditions - along the path of combustion. Depending on the final products, the following types of fermentation are distinguished: 1) alcohol (typical for mushrooms); 2) propionic acid (typical for clostridia, propion bacteria); 3) lactic acid (typical for streptococci); 4) butyric (typical for sarcin); 5) butyldenglycol (typical for bacilli). Along with the main anaerobic breakdown (glycolysis), there may be auxiliary pathways for the breakdown of carbohydrates (pentose phosphate, ketodeoxyphosphogluconate, etc.). They differ in key products and reactions. Lipid metabolism is carried out with the help of enzymes - lipoproteinases, lecitinases, lipases, phospholipases. Lipases catalyze the breakdown of neutral fatty acids, that is, they are responsible for the cleavage of these acids from glycerol. When fatty acids are broken down, the cell stores energy. The final degradation product is acetyl-CoA. Lipid biosynthesis is carried out by acetyl-carrying proteins. In this case, the acetyl residue passes to glycerophosphate with the formation of phosphatidic acids, and they already enter into chemical reactions with the formation of esters with alcohols. These transformations underlie the synthesis of phospholipids. Bacteria are able to synthesize both saturated and unsaturated fatty acids, but the synthesis of the latter is more characteristic of aerobes, since it requires oxygen. Nucleic metabolism of bacteria is associated with genetic metabolism. The synthesis of nucleic acids is important for the process of cell division. Synthesis is carried out with the help of enzymes: restriction enzyme, DNA polymerase, ligase, DNA-dependent RNA polymerase. Restriction enzymes cut out sections of DNA, removing unwanted inserts, and ligases provide cross-linking of nucleic acid fragments. DNA polymerases are responsible for the replication of daughter DNA along the maternal DNA. DNA-dependent RNA polymerases are responsible for transcription and build RNA on a DNA template. LECTURE № 4. Genetics of microorganisms. bacteriophages 1. Organization of the hereditary material of bacteria The hereditary apparatus of bacteria is represented by one chromosome, which is a DNA molecule, it is spiralized and folded into a ring. This ring at one point is attached to the cytoplasmic membrane. Individual genes are located on the bacterial chromosome. The functional units of the bacterial genome, in addition to chromosomal genes, are: 1) IS sequences; 2) transposons; 3) plasmids. IS sequences are short pieces of DNA. They do not carry structural (protein-coding) genes, but contain only genes responsible for transposition (the ability to move along the chromosome and integrate into its various parts). Transposons are larger DNA molecules. In addition to the genes responsible for transposition, they also contain a structural gene. Transposons are able to move along the chromosome. Their position affects gene expression. Transposons can also exist outside the chromosome (autonomously), but are incapable of autonomous replication. Plasmids are additional extrachromosomal genetic material. It is a circular, double-stranded DNA molecule, the genes of which encode additional properties, giving selective advantages to cells. Plasmids are capable of autonomous replication, i.e., independently of the chromosome or under its weak control. Due to autonomous replication, plasmids can give the phenomenon of amplification: the same plasmid can be in several copies, thereby enhancing the manifestation of this feature. Depending on the properties of the features that encode plasmids, there are: 1) R-plasmids. Provide drug resistance; may contain genes responsible for the synthesis of enzymes that destroy medicinal substances, may change the permeability of membranes; 2) F-plasmids. Code for sex in bacteria. Male cells (F+) contain the F-plasmid, female cells (F-) do not. Male cells act as a donor of genetic material during conjugation, while female cells act as a recipient. They differ in surface electric charge and therefore attract. The F-plasmid itself passes from the donor if it is in an autonomous state in the cell. F-plasmids are capable of integrating into the cell chromosome and leaving the integrated state to the autonomous state. In this case, chromosomal genes are captured, which the cell can give during conjugation; 3) Col-plasmids. Code for the synthesis of bacteriocins. These are bactericidal substances that act on closely related bacteria; 4) Tox-plasmids. Encode the production of exotoxins; 5) plasmids biodegradation. Encode enzymes by which bacteria can utilize xenobiotics. The loss of the plasmid by the cell does not lead to its death. Different plasmids can be found in the same cell. 2. Variation in bacteria There are two types of variation - phenotypic and genotypic. Phenotypic variability - modifications - does not affect the genotype. Modifications affect the majority of individuals in a population. They are not inherited and fade over time, i.e., return to the original phenotype. Genotypic variability affects the genotype. It is based on mutations and recombinations. Mutations - a change in the genotype that persists over a number of generations and is accompanied by a change in the phenotype. A feature of mutations in bacteria is the relative ease of their detection. Mutations are distinguished by localization: 1) gene (point); 2) chromosomal; 3) plasmid. By origin, mutations can be: 1) spontaneous (mutagen unknown); 2) induced (mutagen unknown). Recombination is the exchange of genetic material between two individuals with the appearance of recombinant individuals with an altered genotype. Bacteria have several recombination mechanisms: 1) conjugation; 2) fusion of protoplasts; 3) transformation; 4) transduction. Conjugation is the exchange of genetic information through direct contact between the donor and the recipient. The highest frequency of transmission in plasmids, while plasmids can have different hosts. After the formation of a conjugation bridge between the donor and the recipient, one strand of the donor DNA enters the recipient cell through it. The longer this contact, the more of the donor DNA can be transferred to the recipient. Protoplast fusion is a mechanism for the exchange of genetic information through direct contact between sections of the cytoplasmic membrane in bacteria lacking a cell wall. Transformation is the transfer of genetic information in the form of isolated DNA fragments when the recipient cell is in an environment containing donor DNA. Transduction requires a special physiological state of the recipient cell - competence. This state is inherent in actively dividing cells, in which the processes of replication of their own nucleic acids are taking place. In such cells, the competence factor acts - this is a protein that causes an increase in the permeability of the cell wall and cytoplasmic membrane, so a DNA fragment can penetrate into such a cell. Transduction is the transfer of genetic information between bacterial cells by moderate transducing phages. Transducing phages can carry one or more genes. Transduction happens: 1) specific (the same gene is always transferred, the transducing phage is always located in the same place); 2) non-specific (different genes are transmitted, the localization of the transducing phage is not constant). 3. Bacteriophages Bacteriophages (phages) are viruses that infect bacterial cells. They do not have a cellular structure, they are unable to synthesize nucleic acids and proteins themselves, therefore they are obligate intracellular parasites. Phage virions consist of a head containing the nucleic acid of the virus and an outgrowth. The nucleocapsid of the phage head has a cubic type of symmetry, and the process has a spiral type, i.e., bacteriophages have a mixed type of symmetry. Phages can exist in two forms: 1) intracellular (this is a prophage, pure DNA); 2) extracellular (this is a virion). Phages, like other viruses, have antigenic properties and contain group-specific and type-specific antigens. There are two types of interaction between a phage and a cell: 1) lytic (productive viral infection). This is the type of interaction in which the reproduction of the virus occurs in the bacterial cell. She dies at the same time. Phages are first adsorbed on the cell wall. Then comes the penetration phase. Lysozyme acts at the site of phage adsorption, and phage nucleic acid is injected into the cell due to the contractile proteins of the tail. This is followed by an average period during which the synthesis of cellular components is suppressed and the disconjunctive method of phage reproduction is carried out. In this case, the phage nucleic acid is synthesized in the nucleoid region, and then protein synthesis is carried out on the ribosomes. Phages that have a lytic type of interaction are called virulent. In the final period, as a result of self-assembly, proteins fit around the nucleic acid and new phage particles are formed. They leave the cell, breaking its cell wall, i.e., lysis of the bacterium occurs; 2) lysogenic. These are temperate phages. When a nucleic acid penetrates into a cell, it integrates into the cell genome, and a long cohabitation of the phage with the cell is observed without its death. When external conditions change, the phage can leave the integrated form and develop a productive viral infection. A cell containing a prophage in the genome is called lysogenic and differs from the original one by the presence of additional genetic information due to the prophage genes. This is the phenomenon of lysogenic conversion. On the basis of specificity, they distinguish: 1) polyvalent phages (lyse cultures of one family or genus of bacteria); 2) monovalent (lyse cultures of only one type of bacteria); 3) typical (capable of causing lysis of only certain types (variants) of a bacterial culture within a bacterial species). Phages can be used as diagnostic preparations to determine the genus and species of bacteria isolated during bacteriological examination. However, more often they are used for the treatment and prevention of certain infectious diseases. LECTURE No. 5. General virology 1. Morphology and structure of viruses Viruses are microorganisms that make up the Vira kingdom. Features: 1) contain only one type of nucleic acid (RNA or DNA); 2) do not have their own protein-synthesizing and energy systems; 3) do not have a cellular organization; 4) have a disjunctive (separated) mode of reproduction (the synthesis of proteins and nucleic acids occurs in different places and at different times); 5) obligate parasitism of viruses is realized at the genetic level; 6) viruses pass through bacterial filters. Viruses can exist in two forms: extracellular (virion) and intracellular (virus). The shape of the virions can be: 1) rounded; 2) rod-shaped; 3) in the form of regular polygons; 4) filiform, etc. Their sizes range from 15-18 to 300-400 nm. In the center of the virion is a viral nucleic acid covered with a protein coat - a capsid, which has a strictly ordered structure. The capsid is made up of capsomeres. Nucleic acid and capsid make up the nucleocapsid. The nucleocapsid of complexly organized virions is covered with an outer shell - a supercapsid, which can include many functionally different lipid, protein, and carbohydrate structures. The structure of DNA and RNA viruses does not fundamentally differ from the NCs of other microorganisms. Some viruses have uracil in their DNA. DNA can be: 1) double-stranded; 2) single-stranded; 3) ring; 4) double-stranded, but with one shorter chain; 5) double-stranded, but with one continuous and the other fragmented chains. RNA can be: 1) single-strand; 2) linear double-strand; 3) linear fragmented; 4) ring; 5) containing two identical single-stranded RNA. Viral proteins are divided into: 1) genomic - nucleoproteins. Provide replication of viral nucleic acids and virus reproduction processes. These are enzymes, due to which there is an increase in the number of copies of the parent molecule, or proteins, with the help of which molecules are synthesized on the nucleic acid matrix that ensure the implementation of genetic information; 2) proteins of the capsid shell - simple proteins with the ability to self-assemble. They add up to geometrically regular structures, in which several types of symmetry are distinguished: spiral, cubic (form regular polygons, the number of faces is strictly constant) or mixed; 3) proteins of the supercapsid shell are complex proteins, diverse in function. Due to them, the interaction of viruses with a sensitive cell occurs. They perform protective and receptor functions. Among the proteins of the supercapsid shell, there are: a) anchor proteins (at one end they are located on the surface, while at the other they go into the depth; they provide contact of the virion with the cell); b) enzymes (can destroy membranes); c) hemagglutinins (cause hemagglutination); d) elements of the host cell. 2. Interaction of viruses with the host cell The interaction takes place in a single biological system at the genetic level. There are four types of interaction: 1) productive viral infection (interaction resulting in the reproduction of the virus, and the cells die); 2) abortive viral infection (interaction in which the reproduction of the virus does not occur, and the cell restores the impaired function); 3) latent viral infection (there is a reproduction of the virus, and the cell retains its functional activity); 4) virus-induced transformation (an interaction in which a cell infected with a virus acquires new properties that were not previously inherent in it). After adsorption, virions enter the body by endocytosis (viropexis) or by fusion of the viral and cell membranes. The resulting vacuoles containing whole virions or their internal components enter the lysosomes, in which deproteinization is carried out, i.e., the "undressing" of the virus, as a result of which the viral proteins are destroyed. The nucleic acids of viruses freed from proteins penetrate through cell channels into the cell nucleus or remain in the cytoplasm. Nucleic acids of viruses implement the genetic program for the creation of viral offspring and determine the hereditary properties of viruses. With the help of special enzymes (polymerases), copies are made from the parent nucleic acid (replication takes place), and messenger RNAs are synthesized, which are connected to ribosomes and carry out the synthesis of daughter viral proteins (translation). After a sufficient number of virus components accumulate in the infected cell, the assembly of progeny virions begins. This process usually occurs near cell membranes, which sometimes take a direct part in it. The composition of newly formed virions often contains substances characteristic of the cell in which the virus replicates. In such cases, the final step in the formation of virions is their enveloping with a layer of cell membrane. The last step in the interaction of viruses with cells is the release or release of daughter virus particles from the cell. Simple viruses lacking a supercapsid cause cell destruction and enter the intercellular space. Other viruses that have a lipoprotein envelope exit the cell by budding. In this case, the cell remains viable for a long time. In some cases, viruses accumulate in the cytoplasm or nucleus of infected cells, forming crystal-like clusters - inclusion bodies. 3. Cultivation of viruses The main methods of cultivation of viruses: 1) biological - infection of laboratory animals. When infected with a virus, the animal becomes ill. If the disease does not develop, then pathological changes can be detected at autopsy. Animals show immunological changes. However, not all viruses can be cultivated in animals; 2) cultivation of viruses in developing chicken embryos. Chicken embryos are grown in an incubator for 7-10 days and then used for cultivation. In this model, all types of tissue buds are susceptible to infection. But not all viruses can multiply and develop in chicken embryos. As a result of infection, the following can occur and appear: 1) death of the embryo; 2) developmental defects: formations appear on the surface of the membranes - plaques, which are accumulations of dead cells containing virions; 3) accumulation of viruses in the allantoic fluid (detected by titration); 4) reproduction in tissue culture (this is the main method of culturing viruses). There are the following types of tissue cultures: 1) transplanted - cultures of tumor cells; have high mitotic activity; 2) primary trypsinized - subjected to primary treatment with trypsin; this treatment disrupts intercellular communication, resulting in the release of individual cells. The source is any organs and tissues, most often - embryonic (have a high mitotic activity). Special media are used to maintain tissue culture cells. These are liquid nutrient media of complex composition containing amino acids, carbohydrates, growth factors, protein sources, antibiotics and indicators for assessing the development of tissue culture cells. The reproduction of viruses in tissue culture is judged by their cytopathic action, which is of a different nature depending on the type of virus. The main manifestations of the cytopathic action of viruses: 1) virus reproduction may be accompanied by cell death or morphological changes in them; 2) some viruses cause cell fusion and the formation of multinuclear syncytium; 3) cells can grow, but divide, resulting in the formation of giant cells; 4) inclusions appear in the cells (nuclear, cytoplasmic, mixed). Inclusions may stain pink (eosinophilic inclusions) or blue (basophilic inclusions); 5) if viruses containing hemagglutinins multiply in tissue culture, then in the process of reproduction the cell acquires the ability to adsorb erythrocytes (hemadsorption). 4. Features of antiviral immunity Antiviral immunity begins with the presentation of the viral antigen by T-helpers. Dendritic cells have strong antigen-presenting properties in viral infections, and Langerhans cells in herpes simplex and retroviral infections. Immunity is aimed at neutralizing and removing the virus, its antigens and virus-infected cells from the body. Antibodies formed during viral infections act directly on the virus or on cells infected by it. In this regard, there are two main forms of participation of antibodies in the development of antiviral immunity: 1) neutralization of the virus with antibodies; this prevents the reception of the virus by the cell and its penetration inside. Opsonization of the virus with antibodies promotes its phagocytosis; 2) immune lysis of virus-infected cells with the participation of antibodies. When antibodies act on antigens expressed on the surface of an infected cell, complement is added to this complex, followed by its activation, which causes the induction of complement-dependent cytotoxicity and the death of the virus-infected cell. Insufficient concentration of antibodies can enhance the reproduction of the virus. Sometimes antibodies can protect the virus from the action of proteolytic enzymes of the cell, which, while maintaining the viability of the virus, leads to an increase in its replication. Virus-neutralizing antibodies act directly on the virus only when it, having destroyed one cell, spreads to another. When viruses pass from cell to cell along cytoplasmic bridges without contact with circulating antibodies, the main role in the development of immunity is played by cellular mechanisms associated primarily with the action of specific cytotoxic T-lymphocytes, T-effectors, and macrophages. Cytotoxic T-lymphocytes directly contact the target cell, increasing its permeability and causing osmotic swelling, membrane rupture and release of contents into the environment. The mechanism of the cytotoxic effect is associated with the activation of membrane enzyme systems in the area of cell adhesion, the formation of cytoplasmic bridges between cells, and the action of lymphotoxin. Specific T-killers appear within 1-3 days after infection with the virus, their activity reaches a maximum after a week, and then slowly decreases. One of the factors of antiviral immunity is interferon. It is formed at the sites of virus reproduction and causes specific inhibition of the transcription of the viral genome and suppression of the translation of viral mRNA, which prevents the accumulation of the virus in the target cell. The persistence of antiviral immunity is variable. With a number of infections (chicken pox, mumps, measles, rubella), immunity is quite stable, and repeated diseases are extremely rare. Less stable immunity develops with infections of the respiratory tract (flu) and intestinal tract. LECTURE No. 6. The doctrine of infection 1. General characteristics of the infection Infection is a set of biological reactions with which a macroorganism responds to the introduction of a pathogen. The range of manifestations of infections can be different. Extreme forms of manifestation of infections are: 1) bacteriocarrier, persistence, live vaccination; 2) infectious disease; there are clinical manifestations of infection, these reactions can be fatal. The infectious process is the response of the population collective to the introduction and circulation of microbial agents in it. Infectious diseases have a number of characteristic features that distinguish them from other diseases: 1) infectious diseases have their own pathogen - a microorganism; 2) infectious diseases are contagious, that is, they are capable of being transmitted from a patient to a healthy person; 3) infectious diseases leave behind a more or less pronounced immunity or hypersensitivity to this disease; 4) infectious diseases are characterized by a number of common signs: fever, symptoms of general intoxication, lethargy, weakness; 5) infectious diseases have a clearly defined staging, phasing. For the occurrence of an infectious disease, a combination of the following factors is necessary: 1) the presence of a microbial agent; 2) susceptibility of the macroorganism; 3) the presence of an environment in which this interaction takes place. The microbial agent is pathogenic and opportunistic microorganisms. Essential for the occurrence of an infectious disease is the infectious dose of the pathogen - the minimum number of microbial cells that can cause an infectious process. Infective doses depend on the species of the pathogen, its virulence and the state of nonspecific and immune defenses. Tissues deprived of physiological protection against a particular type of microorganism serve as a place for its penetration into the macroorganism, or as an entrance gate for infection. The entrance gate determines the localization of the pathogen in the body, pathogenetic and clinical features of the disease. The external environment can influence both the macroorganism and pathogenic microbes. These are natural-climatic, socio-economic, cultural and living conditions. A number of infections are characterized by epidemics and pandemics. An epidemic is a widespread infection in a population covering large areas, characterized by the mass nature of diseases. Pandemic - the spread of infection to almost the entire territory of the globe with a very high percentage of cases of disease. Endemic diseases (with natural foci) are diseases for which territorial areas with an increased incidence of this infection are noted. 2. Forms of infection and periods of infectious diseases Classification of infections 1. By etiology: 1) bacterial; 2) viral; 3) protozoan; 4) mycoses; 5) mixed infections. 2. By the number of pathogens: 1) monoinfections; 2) polyinfections. 3. According to the severity of the course: 1) lungs; 2) heavy; 3) moderate. 4. By duration: 1) sharp; 2) subacute; 3) chronic; 4) latent. 5. By means of transmission: 1) horizontal: a) airborne route; b) fecal-oral; c) contact; d) transmissive; e) sexual; 2) vertical: a) from mother to fetus (transplacental); b) from mother to newborn in the birth act; 3) artificial (artificial) - with injections, examinations, operations, etc. Depending on the location of the pathogen, there are: 1) focal infection, in which microorganisms are localized in a local focus and do not spread throughout the body; 2) a generalized infection, in which the pathogen spreads throughout the body by lymphogenous and hematogenous routes. In this case, bacteremia or viremia develops. The most severe form is sepsis. Also distinguish: 1) exogenous infections; arise as a result of human infection with pathogenic microorganisms coming from the environment with food, water, air, soil, secretions of a sick person, a convalescent person and a microcarrier; 2) endogenous infections; are caused by representatives of normal microflora - conditionally pathogenic microorganisms of the individual himself. A variety of endogenous infections - autoinfections, they arise as a result of self-infection by transferring the pathogen from one biotope to another. The following periods of infectious diseases are distinguished: 1) incubation; from the moment the pathogen enters the body until the first signs of the disease appear. Duration - from several hours to several weeks. The patient is not contagious; 2) prodromal; characterized by the appearance of the first unclear general symptoms. The causative agent multiplies intensively, colonizes the tissue, begins to produce enzymes and toxins. Duration - from several hours to several days; 3) the height of the disease; characterized by specific symptoms. The causative agent continues to multiply intensively, accumulate, release toxins and enzymes into the blood. There is a release of the pathogen from the body, so the patient is a danger to others. At the beginning of this period, specific antibodies are detected in the blood; 4) outcome. There may be different options: a) lethal outcome; b) recovery (clinical and microbiological). Clinical recovery: the symptoms of the disease have subsided, but the pathogen is still in the body. This option is dangerous by the formation of carriage and relapse of the disease. Microbiological - complete recovery; c) chronic carriage. Reinfection is a disease that occurs after an infection in case of re-infection with the same pathogen. Superinfection occurs when, against the background of the course of one infectious disease, infection with another pathogen occurs. 3. Infectious agents and their properties Bacteria are distinguished by their ability to cause disease: 1) pathogenic; 2) conditionally pathogenic; 3) saprophytic. Pathogenic species have the potential to cause an infectious disease. Pathogenicity is the ability of microorganisms, entering the body, to cause pathological changes in its tissues and organs. This is a qualitative species trait determined by pathogenicity genes - virulons. They can be localized in chromosomes, plasmids, transposons. Conditionally pathogenic bacteria can cause an infectious disease when the body's defenses are reduced. Saprophytic bacteria never cause disease, since they are not able to multiply in the tissues of the macroorganism. The implementation of pathogenicity goes through virulence - this is the ability of a microorganism to penetrate into a macroorganism, multiply in it and suppress its protective properties. This is a strain trait, it can be quantified. Virulence is the phenotypic manifestation of pathogenicity. The quantitative characteristics of virulence are: 1) DLM (minimum lethal dose) is the amount of bacteria, which, when introduced into the body of laboratory animals in an appropriate way, results in 95-98% of the death of animals in the experiment; 2) LD 50 is the number of bacteria that causes the death of 50% of the animals in the experiment; 3) DCL (lethal dose) causes 100% death of animals in the experiment. Virulence factors include: 1) adhesion - the ability of bacteria to attach to epithelial cells. Adhesion factors are adhesion cilia, adhesive proteins, lipopolysaccharides in gram-negative bacteria, teichoic acids in gram-positive bacteria, in viruses - specific structures of a protein or polysaccharide nature; 2) colonization - the ability to multiply on the surface of cells, which leads to the accumulation of bacteria; 3) penetration - the ability to penetrate cells; 4) invasion - the ability to penetrate into the underlying tissues. This ability is associated with the production of enzymes such as hyaluronidase and neuraminidase; 5) aggression - the ability to resist the factors of non-specific and immune defense of the body. Aggressive factors include: 1) substances of various nature that make up the surface structures of the cell: capsules, surface proteins, etc. Many of them inhibit the migration of leukocytes, preventing phagocytosis; 2) enzymes - proteases, coagulase, fibrinolysin, lecithinase; 3) toxins, which are divided into exo- and endotoxins. Exotoxins are highly toxic proteins. They are thermolabile, they are strong antigens, for which antibodies are produced in the body, which enter into toxin neutralization reactions. This trait is encoded by plasmids or prophage genes. Endotoxins are complex complexes of lipopolysaccharide nature. They are thermostable, are weak antigens, have a general toxic effect. Encoded by chromosomal genes. LECTURE No. 7. Normal microflora of the human body 1. Normal human microflora The normal human microflora is a combination of many microbiocenoses characterized by certain relationships and habitats. In the human body, in accordance with the living conditions, biotopes with certain microbiocenoses are formed. Any microbiocenosis is a community of microorganisms that exists as a whole, connected by food chains and microecology. Types of normal microflora: 1) resident - permanent, characteristic of a given species; 2) transient - temporarily trapped, uncharacteristic for a given biotope; She doesn't actively reproduce. Normal microflora is formed from birth. Its formation is influenced by the microflora of the mother and the nosocomial environment, the nature of feeding. Factors affecting the state of normal microflora. 1. Endogenous: 1) secretory function of the body; 2) hormonal background; 3) acid-base state. 2. Exogenous conditions of life (climatic, domestic, environmental). Microbial contamination is typical for all systems that have contact with the environment. In the human body, blood, cerebrospinal fluid, articular fluid, pleural fluid, thoracic duct lymph, internal organs: heart, brain, liver parenchyma, kidneys, spleen, uterus, bladder, lung alveoli are sterile. Normal microflora lines the mucous membranes in the form of a biofilm. This polysaccharide scaffold consists of microbial cell polysaccharides and mucin. It contains microcolonies of cells of normal microflora. The thickness of the biofilm is 0,1-0,5 mm. It contains from several hundred to several thousand microcolonies. The formation of a biofilm for bacteria creates additional protection. Inside the biofilm, bacteria are more resistant to chemical and physical factors. Stages of formation of normal microflora of the gastrointestinal tract (GIT): 1) accidental seeding of the mucosa. Lactobacilli, clostridia, bifidobacteria, micrococci, staphylococci, enterococci, Escherichia coli, etc. enter the gastrointestinal tract; 2) the formation of a network of tape bacteria on the surface of the villi. Mostly rod-shaped bacteria are fixed on it, the process of biofilm formation is constantly going on. The normal microflora is considered as an independent extracorporeal organ with a specific anatomical structure and functions. Functions of normal microflora: 1) participation in all types of exchange; 2) detoxification in relation to exo- and endoproducts, transformation and release of medicinal substances; 3) participation in the synthesis of vitamins (groups B, E, H, K); 4) protection: a) antagonistic (associated with the production of bacteriocins); b) colonization resistance of mucous membranes; 5) immunogenic function. The highest contamination is characterized by: 1) large intestine; 2) oral cavity; 3) urinary system; 4) upper respiratory tract; 5) skin. 2. Dysbacteriosis Dysbacteriosis (dysbiosis) is any quantitative or qualitative changes in the normal human microflora typical for a given biotope, resulting from the impact of various unfavorable factors on a macro- or microorganism. Microbiological indicators of dysbiosis are: 1) decrease in the number of one or more permanent species; 2) the loss of certain traits by bacteria or the acquisition of new ones; 3) increase in the number of transient species; 4) the emergence of new species unusual for this biotope; 5) weakening of the antagonistic activity of normal microflora. The reasons for the development of dysbacteriosis can be: 1) antibiotic and chemotherapy; 2) severe infections; 3) severe somatic diseases; 4) hormone therapy; 5) radiation exposure; 6) toxic factors; 7) deficiency of vitamins. Dysbacteriosis of different biotopes has different clinical manifestations. Intestinal dysbacteriosis can manifest itself in the form of diarrhea, nonspecific colitis, duodenitis, gastroenteritis, chronic constipation. Respiratory dysbacteriosis occurs in the form of bronchitis, bronchiolitis, chronic lung diseases. The main manifestations of oral dysbiosis are gingivitis, stomatitis, caries. Dysbacteriosis of the reproductive system in women proceeds as vaginosis. Depending on the severity of these manifestations, several phases of dysbacteriosis are distinguished: 1) compensated, when dysbacteriosis is not accompanied by any clinical manifestations; 2) subcompensated, when local inflammatory changes occur as a result of an imbalance in the normal microflora; 3) decompensated, in which the process is generalized with the appearance of metastatic inflammatory foci. Laboratory diagnosis of dysbacteriosis The main method is bacteriological research. At the same time, quantitative indicators prevail in the evaluation of its results. Not specific identification is carried out, but only to the genus. An additional method is chromatography of the spectrum of fatty acids in the material under study. Each genus has its own spectrum of fatty acids. Correction of dysbacteriosis: 1) elimination of the cause that caused the imbalance of normal microflora; 2) the use of eubiotics and probiotics. Eubiotics are preparations containing live bactericinogenic strains of normal microflora (colibacterin, bifidumbacterin, bifikol, etc.). Probiotics are substances of non-microbial origin and foods containing additives that stimulate their own normal microflora. Stimulants - oligosaccharides, casein hydrolyzate, mucin, whey, lactoferrin, dietary fiber. LECTURE No. 8. Antibiotics and chemotherapy 1. Chemotherapy drugs Chemotherapeutic drugs are medicinal substances used to suppress vital activity and destroy microorganisms in the tissues and environments of the patient, which have a selective, etiotropic (acting on the cause) effect. According to the direction of action, chemotherapeutic drugs are divided into: 1) antiprotozoal; 2) antifungal; 3) antiviral; 4) antibacterial. According to the chemical structure, several groups of chemotherapeutic drugs are distinguished: 1) sulfa drugs (sulfonamides) - derivatives of sulfanilic acid. They disrupt the process of obtaining microbes necessary for their life and development of growth factors - folic acid and other substances. This group includes streptocid, norsulfazol, sulfametizol, sulfamethaxazole, etc.; 2) derivatives of nitrofuran. The mechanism of action is to block several enzyme systems of the microbial cell. These include furatsilin, furagin, furazolidone, nitrofurazon, etc.; 3) quinolones. Violate various stages of DNA synthesis of a microbial cell. These include nalidixic acid, cinoxacin, norfloxacin, ciprofloxacin; 4) azoles - imidazole derivatives. They have antifungal activity. They inhibit the biosynthesis of steroids, which leads to damage to the outer cell membrane of fungi and an increase in its permeability. These include clotrimazole, ketoconazole, fluconazole, etc.; 5) diaminopyrimidines. Violate the metabolism of microbial cells. These include trimethoprim, pyrimethamine; 6) antibiotics are a group of compounds of natural origin or their synthetic analogues. Principles of classification of antibiotics. 1. According to the mechanism of action: 1) violating the synthesis of the microbial wall (b-lactam antibiotics; cycloserine; vancomycin, teikoplakin); 2) disrupting the functions of the cytoplasmic membrane (cyclic polypeptides, polyene antibiotics); 3) disrupting the synthesis of proteins and nucleic acids (a group of levomycetin, tetracycline, macrolides, lincosamides, aminoglycosides, fusidine, ansamycins). 2. By type of action on microorganisms: 1) antibiotics with a bactericidal effect (affecting the cell wall and cytoplasmic membrane); 2) antibiotics with bacteriostatic action (affecting the synthesis of macromolecules). 3. According to the spectrum of action: 1) with a predominant effect on gram-positive microorganisms (lincosamides, biosynthetic penicillins, vancomycin); 2) with a predominant effect on gram-negative microorganisms (monobactams, cyclic polypeptides); 3) a wide spectrum of action (aminoglycosides, chloramphenicol, tetracyclines, cephalosporins). 4. By chemical structure: 1) b-lactam antibiotics. These include: a) penicillins, among which are natural (aminipenicillin) and semi-synthetic (oxacillin); b) cephalosporins (ceporin, cefazolin, cefotaxime); c) monobactams (primbactam); d) carbapenems (imipinem, meropinem); 2) aminoglycosides (kanamycin, neomycin); 3) tetracyclines (tetracycline, metacycline); 4) macrolides (erythromycin, azithromycin); 5) lincosamines (lincomycin, clindamycin); 6) polyenes (amphotericin, nystatin); 7) glycopeptides (vancomycin, teikoplakin). 2. Main complications of chemotherapy All complications of chemotherapy can be divided into two groups: complications from the macroorganism and from the microorganism. Complications from the microorganism: 1) allergic reactions. The severity can be different - from mild forms to anaphylactic shock. The presence of an allergy to one of the drugs in the group is a contraindication for the use of other drugs in this group, since cross-sensitivity is possible; 2) direct toxic effect. Aminoglycosides have ototoxicity and nephrotoxicity, tetracyclines disrupt the formation of bone tissue and teeth. Ciprofloxacin can have a neurotoxic effect, fluoroquinolones can cause arthropathy; 3) side toxic effects. These complications are not associated with a direct, but with an indirect effect on various body systems. Antibiotics that affect protein synthesis and nucleic acid metabolism always depress the immune system. Chloramphenicol can inhibit protein synthesis in bone marrow cells, causing lymphopenia. Furagin, penetrating the placenta, can cause hemolytic anemia in the fetus; 4) aggravation reactions. When using chemotherapeutic agents in the first days of the disease, mass death of pathogens can occur, accompanied by the release of a large amount of endotoxin and other decay products. This may be accompanied by a deterioration in the condition up to toxic shock. These reactions are more common in children. Therefore, antibiotic therapy should be combined with detoxification measures; 5) development of dysbiosis. It often occurs against the background of the use of broad-spectrum antibiotics. Complications from the microorganism are manifested by the development of drug resistance. It is based on mutations in chromosomal genes or the acquisition of resistance plasmids. There are genera of microorganisms that are naturally resistant. The biochemical basis of resistance is provided by the following mechanisms: 1) enzymatic inactivation of antibiotics. This process is provided with the help of enzymes synthesized by bacteria that destroy the active part of antibiotics; 2) a change in the permeability of the cell wall for the antibiotic or suppression of its transport into bacterial cells; 3) change in the structure of microbial cell components. The development of one or another mechanism of resistance depends on the chemical structure of the antibiotic and the properties of bacteria. Methods for combating drug resistance: 1) search and creation of new chemotherapeutic drugs; 2) the creation of combined drugs, which include chemotherapeutic agents of various groups that enhance the effect of each other; 3) periodic change of antibiotics; 4) compliance with the basic principles of rational chemotherapy: a) antibiotics should be prescribed in accordance with the sensitivity of pathogens to them; b) treatment should be started as early as possible; c) chemotherapeutic drugs must be prescribed in maximum doses, preventing microorganisms from adapting. LECTURE No. 9. Introduction to immunology 1. The concept of immunity. Types of immunity Immunology is a science whose subject of study is immunity. Infectious immunology studies the patterns of the immune system in relation to microbial agents, specific mechanisms of antimicrobial protection. Immunity is understood as a set of biological phenomena aimed at maintaining the constancy of the internal environment and protecting the body from infectious and other genetically alien agents. The manifestations of immunity are diverse. Its main task is to recognize a foreign agent. Immunity can be infectious, antitumor, transplantation. Immunity is provided by the work of the immune system, it is based on specific mechanisms. Types of infectious immunity: 1) antibacterial; 2) antitoxic; 3) antiviral; 4) antifungal; 5) antiprotozoal. Infectious immunity can be: 1) sterile (there is no pathogen in the body, but there is resistance to it); 2) non-sterile (the pathogen is in the body). There are congenital and acquired, active and passive, specific and individual immunity. Innate immunity to infectious diseases is present from birth. It can be specific and individual. Species immunity is the immunity of one species of animal or person to microorganisms that cause disease in other species. It is genetically determined in humans as a biological species, i.e. a person does not suffer from zoonotic diseases. Species immunity is always active. Individual innate immunity is passive, as it is provided by the transfer of immunoglobulins to the fetus from the mother through the placenta (placental immunity). Thus, the newborn is protected from infections that the mother has had. Acquired immunity is called such immunity of the human body to infectious agents, which is formed in the process of its individual development and is characterized by strict specificity. It is always individual. It can be natural and artificial. Natural immunity can be: 1) active. Formed after an infection; post-infection immunity can persist for a long time, sometimes throughout life; 2) passive. Immunoglobulins of class A and I are transmitted to the child with mother's milk. Artificial immunity can be created actively and passively. Active is formed by the introduction of antigenic preparations, vaccines, toxoids. Passive immunity is formed by the introduction of ready-made sera and immunoglobulins, i.e. ready-made antibodies. The creation of immunity underlies the specific immunoprophylaxis of infectious diseases. 2. Non-specific protective factors Anti-infective protection is carried out: 1) skin and mucous membranes; 2) lymph nodes; 3) lysozyme and other enzymes of the oral cavity and gastrointestinal tract; 4) normal microflora; 5) inflammation; 6) phagocytic cells; 7) natural killers; 8) complement system; 9) interferons. Intact skin and mucous membranes are a barrier that prevents the penetration of microorganisms into the body. As a result of desquamation of the epidermis, many transient microorganisms are removed. The secret of sweat and sebaceous glands has bactericidal properties. In the presence of injuries, burns, the skin forms an entrance gate for infection. Secrets secreted by the mucous membranes, salivary and digestive glands, tears wash off microorganisms from the surface of the mucous membranes, have a bactericidal effect. Lysozyme is a protein found in tissue fluids, plasma, blood serum, leukocytes, breast milk, etc. It causes bacterial lysis and is inactive against viruses. Representatives of the normal microflora can act as antagonists of pathogenic microorganisms, preventing their introduction and reproduction. Inflammation is a protective function of the body. It limits the focus of infection at the site of the entrance gate. The leading link in the development of inflammation is phagocytosis. Completed phagocytosis is a protective function of the body. There are the following stages of phagocytosis: 1) attraction; 2) adhesion; 3) endocytosis; 4) killing; 5) elimination. If the last two stages are absent, then this is an incomplete phagocytosis. In this case, the process loses its protective function, the bacteria inside the macrophages are carried throughout the body. Natural killers - a population of cells with natural cytotoxicity in relation to target cells. Morphologically, they are large granular lymphocytes. They are cells with effector antitumor, antiviral and antiparasitic activity. Complement is a system of non-specific serum proteins, consisting of nine fractions. Activating one faction activates the next faction. It has a bactericidal effect, as it has an affinity for the surface structures of a bacterial cell and, together with lysozyme, can cause cytolysis. Interferons are proteins that have antiviral, antitumor, immunomodulatory effects. Interferon acts by regulating the synthesis of nucleic acids and proteins, activating the synthesis of enzymes and inhibitors that block the translation of viral and RNA. As a rule, it does not save a cell already infected with a virus, but it protects neighboring cells from a viral infection. LECTURE No. 10. The immune system of the human body 1. Central and peripheral organs of the immune system The human immune system provides specific protection of the body from genetically alien molecules and cells, including infectious agents - bacteria, viruses, fungi, protozoa. Lymphoid cells mature and function in specific organs. The organs of the immune system are divided into: 1) primary (central); the thymus gland, bone marrow are the sites of differentiation of lymphocyte populations; 2) secondary (peripheral); the spleen, lymph nodes, tonsils, lymphoid tissue associated with the intestines and bronchi are populated by B- and T-lymphocytes from the central organs of the immune system; after contact with the antigen in these organs, lymphocytes are included in the recycling. The thymus gland (thymus) plays a leading role in the regulation of the population of T-lymphocytes. The thymus supplies lymphocytes, which the embryo needs for the growth and development of lymphoid organs and cell populations in various tissues. Differentiating, lymphocytes, due to the release of humoral substances, receive antigenic markers. The cortical layer is densely filled with lymphocytes, which are affected by thymic factors. In the medulla there are mature T-lymphocytes that leave the thymus and are included in the circulation as T-helpers, T-killers, T-suppressors. The bone marrow supplies progenitor cells for various populations of lymphocytes and macrophages, and specific immune responses take place in it. It serves as the main source of serum immunoglobulins. The spleen is colonized by lymphocytes in the late embryonic period after birth. In the white pulp there are thymus-dependent and thymus-independent zones, which are populated by T- and B-lymphocytes. Antigens entering the body induce the formation of lymphoblasts in the thymus-dependent zone of the spleen, and in the thymus-independent zone, proliferation of lymphocytes and the formation of plasma cells are noted. Lymphocytes enter the lymph nodes through afferent lymphatic vessels. The movement of lymphocytes between tissues, the bloodstream and lymph nodes allows antigen-sensitive cells to detect the antigen and accumulate in those places where the immune reaction occurs, and the spread of memory cells and their descendants throughout the body allows the lymphoid system to organize a generalized immune response. The lymphatic follicles of the digestive tract and respiratory system serve as the main entry gate for antigens. In these organs, there is a close relationship between lymphoid cells and endothelium, as in the central organs of the immune system. 2. Cells of the immune system Immunocompetent cells of the human body are T- and B-lymphocytes. T-lymphocytes originate in the embryonic thymus. In the postembryonic period after maturation, T-lymphocytes settle in T-zones of peripheral lymphoid tissue. After stimulation (activation) with a certain antigen, T-lymphocytes are transformed into large transformed T-lymphocytes, from which the executive link of T-cells then arises. T cells are involved in: 1) cellular immunity; 2) regulation of B-cell activity; 3) delayed hypersensitivity (IV) type. The following subpopulations of T-lymphocytes are distinguished: 1) T-helpers. Programmed to induce proliferation and differentiation of other cell types. They induce the secretion of antibodies by B-lymphocytes and stimulate monocytes, mast cells and T-killer progenitors to participate in cellular immune responses. This subpopulation is activated by antigens associated with class II MHC gene products, class II molecules present predominantly on the surface of B cells and macrophages; 2) suppressor T cells. Genetically programmed for suppressive activity, they respond mainly to class I MHC gene products. They bind antigen and secrete factors that inactivate T-helpers; 3) T-killers. They recognize the antigen in combination with their own class I MHC molecules. They secrete cytotoxic lymphokines. The main function of B-lymphocytes is that, in response to an antigen, they are able to multiply and differentiate into plasma cells that produce antibodies. B-lymphocytes are divided into two subpopulations: B1 and B2. B1-lymphocytes undergo primary differentiation in Peyer's patches, then they are found on the surface of serous cavities. During the humoral immune response, they are able to turn into plasma cells that synthesize only IgM. T-helpers are not always needed for their transformation. B2-lymphocytes undergo differentiation in the bone marrow, then in the red pulp of the spleen and lymph nodes. Their transformation into plasma cells occurs with the participation of T-helpers. Such plasma cells are capable of synthesizing all classes of human Ig. Memory B-cells are long-lived B-lymphocytes derived from mature B-cells as a result of antigen stimulation with the participation of T-lymphocytes. When re-stimulated with antigen, these cells are activated much more easily than the original B cells. They provide (with the participation of T-cells) the rapid synthesis of a large number of antibodies upon repeated penetration of the antigen into the body. Macrophages are distinct from lymphocytes but also play an important role in the immune response. They can be: 1) antigen-processing cells when a response occurs; 2) phagocytes in the form of an executive link. 3. Forms of the immune response The immune response is a chain of successive complex cooperative processes that occur in the immune system in response to the action of an antigen in the body. Distinguish: 1) primary immune response (occurs at the first meeting with the antigen); 2) secondary immune response (occurs upon repeated encounter with the antigen). Any immune response consists of two phases: 1) inductive; presentation and recognition of the antigen. There is a complex cooperation of cells with subsequent proliferation and differentiation; 2) productive; products of the immune response are found. With a primary immune response, the inductive phase can last a week, with a secondary one - up to 3 days due to memory cells. In the immune response, antigens that enter the body interact with antigen-presenting cells (macrophages), which express antigenic determinants on the cell surface and deliver information about the antigen to the peripheral organs of the immune system, where T-helpers are stimulated. Further, the immune response is possible in the form of one of three options: 1) cellular immune response; 2) humoral immune response; 3) immunological tolerance. The cellular immune response is a function of T-lymphocytes. There is the formation of effector cells - T-killers, capable of destroying cells that have an antigenic structure by direct cytotoxicity and by the synthesis of lymphokines, which are involved in the processes of cell interaction (macrophages, T-cells, B-cells) during the immune response. Two subtypes of T cells are involved in the regulation of the immune response: T-helpers enhance the immune response, T-suppressors have the opposite effect. Humoral immunity is a function of B cells. T-helpers that have received antigenic information transmit it to B-lymphocytes. B-lymphocytes form a clone of antibody-producing cells. In this case, B-cells are converted into plasma cells that secrete immunoglobulins (antibodies) that have specific activity against the introduced antigen. The resulting antibodies interact with the antigen with the formation of an AG-AT complex, which triggers nonspecific mechanisms of a protective reaction. These complexes activate the complement system. The interaction of the AG-AT complex with mast cells leads to degranulation and the release of inflammatory mediators - histamine and serotonin. At a low dose of the antigen, immunological tolerance develops. In this case, the antigen is recognized, but as a result of this, neither cell production nor the development of a humoral immune response occurs. The immune response is characterized by: 1) specificity (reactivity is directed only to a specific agent, which is called an antigen); 2) potentiation (the ability to produce an enhanced response with a constant intake of the same antigen in the body); 3) immunological memory (the ability to recognize and produce an enhanced response against the same antigen when it enters the body again, even if the first and subsequent hits occur at long intervals). LECTURE No. 11. Antigens 1. Properties and types of antigens Antigens are high molecular weight compounds. When ingested, they cause an immune reaction and interact with the products of this reaction: antibodies and activated lymphocytes. Classification of antigens. 1. By origin: 1) natural (proteins, carbohydrates, nucleic acids, bacterial exo- and endotoxins, tissue and blood cell antigens); 2) artificial (dinitrophenylated proteins and carbohydrates); 3) synthetic (synthesized polyamino acids, polypeptides). 2. By chemical nature: 1) proteins (hormones, enzymes, etc.); 2) carbohydrates (dextran); 3) nucleic acids (DNA, RNA); 4) conjugated antigens (dinitrophenyl proteins); 5) polypeptides (polymers of a-amino acids, copolymers of glutamine and alanine); 6) lipids (cholesterol, lecithin, which can act as a hapten, but when combined with blood serum proteins, they acquire antigenic properties). 3. By genetic relation: 1) autoantigens (come from the tissues of one's own body); 2) isoantigens (come from a genetically identical donor); 3) alloantigens (come from an unrelated donor of the same species); 4) xenoantigens (come from a donor of another species). 4. By the nature of the immune response: 1) thymus-dependent antigens (the immune response depends on the active participation of T-lymphocytes); 2) thymus-independent antigens (trigger the immune response and the synthesis of antibodies by B-cells without T-lymphocytes). Also distinguish: 1) external antigens; enter the body from outside. These are microorganisms, transplanted cells and foreign particles that can enter the body by alimentary, inhalation or parenteral routes; 2) internal antigens; arise from damaged body molecules that are recognized as foreign; 3) latent antigens - certain antigens (for example, nervous tissue, lens proteins and spermatozoa); anatomically separated from the immune system by histohematic barriers during embryogenesis; tolerance to these molecules does not occur; their entry into the bloodstream can lead to an immune response. Immunological reactivity against altered or hidden self antigens occurs in some autoimmune diseases. Properties of antigens: 1) antigenicity - the ability to cause the formation of antibodies; 2) immunogenicity - the ability to create immunity; 3) specificity - antigenic features, due to the presence of which antigens differ from each other. Haptens are low molecular weight substances that under normal conditions do not cause an immune response, but when bound to high molecular weight molecules become immunogenic. Haptens include drugs and most chemicals. They are able to induce an immune response after binding to body proteins. Antigens or haptens that cause an allergic reaction when re-introduced into the body are called allergens. 2. Antigens of microorganisms Infectious antigens are antigens of bacteria, viruses, fungi, protozoa. There are the following types of bacterial antigens: 1) group-specific (found in different species of the same genus or family); 2) species-specific (found in different representatives of the same species); 3) type-specific (determine serological variants - serovars, antigenovars - within one species). Depending on the localization in the bacterial cell, there are: 1) O - AG - polysaccharide; is part of the bacterial cell wall. Determines the antigenic specificity of cell wall lipopolysaccharide; it distinguishes serovariants of bacteria of the same species. O - AG is weakly immunogenic. It is thermally stable (withstands boiling for 1-2 hours), chemically stable (withstands treatment with formalin and ethanol); 2) lipid A - heterodimer; contains glucosamine and fatty acids. It has strong adjuvant, non-specific immunostimulatory activity and toxicity; 3) H - AG; is part of bacterial flagella, its basis is the flagellin protein. Thermolabile; 4) K - AG - a heterogeneous group of surface, capsular antigens of bacteria. They are encapsulated and associated with the surface layer of lipopolysaccharide of the cell wall; 5) toxins, nucleoproteins, ribosomes and bacterial enzymes. Virus antigens: 1) supercapsid antigens - surface shell; 2) protein and glycoprotein antigens; 3) capsid - shell; 4) nucleoprotein (core) antigens. All viral antigens are T-dependent. Protective antigens are a set of antigenic determinants (epitopes) that cause the strongest immune response, which protects the body from re-infection with this pathogen. Ways of penetration of infectious antigens into the body: 1) through damaged and sometimes intact skin; 2) through the mucous membranes of the nose, mouth, gastrointestinal tract, urinary tract. Heteroantigens are antigenic complexes common to representatives of different species or common antigenic determinants on complexes that differ in other properties. Due to heteroantigens, immunological cross-reactions can occur. In microbes of various species and in humans, there are common antigens similar in structure. These phenomena are called antigenic mimicry. Superantigens are a special group of antigens that in very small doses cause polyclonal activation and proliferation of a large number of T-lymphocytes. Superantigens are bacterial enterotoxins, staphylococcal, cholera toxins, some viruses (rotaviruses). LECTURE No. 12. Antibodies 1. Structure of immunoglobulins Antibodies (immunoglobulins) are proteins that are synthesized under the influence of an antigen and specifically react with it. They are made up of polypeptide chains. There are four structures in the immunoglobulin molecule: 1) primary - this is the sequence of certain amino acids. It is built from nucleotide triplets, is genetically determined and determines the main subsequent structural features; 2) secondary (determined by the conformation of polypeptide chains); 3) tertiary (determines the nature of the location of individual sections of the chain that create a spatial picture); 4) Quaternary. A biologically active complex arises from four polypeptide chains. Chains in pairs have the same structure. Most immunoglobulin molecules are composed of two heavy (H) chains and two light (L) chains linked by disulfide bonds. Light chains consist of either two k-chains or two l-chains. Heavy chains can be one of five classes (IgA, IgG, IgM, IgD and IgE). Each circuit has two sections: 1) permanent. Remains constant in amino acid sequence and antigenicity within a given immunoglobulin class; 2) variable. It is characterized by a large inconsistency in the sequence of amino acids; in this part of the chain, the reaction of the compound with the antigen occurs. Each IgG molecule consists of two connected chains, the ends of which form two antigen-binding sites. The variable region of each chain has hypervariable regions: three in the light chains and four in the heavy chains. The amino acid sequence variations in these hypervariable regions determine the specificity of the antibody. Under certain conditions, these hypervariable regions can also act as antigens (idiotypes). There cannot be less than two antigen-binding centers in an immunoglobulin molecule, but one can be wrapped inside the molecule - this is an incomplete antibody. It blocks the antigen so that it cannot bind to the full antibodies. During the enzymatic cleavage of immunoglobulins, the following fragments are formed: 1) Fc-fragment contains sections of both permanent parts; does not have the property of an antibody, but has an affinity for complement; 2) Fab-fragment contains light and part of the heavy chain with a single antigen-binding site; has the property of an antibody; 3) F(ab)T2-fragment consists of two interconnected Fab-fragments. Other classes of immunoglobulins have the same basic structure. The exception is IgM: it is a pentamer (consists of five basic units connected in the region of Fc ends), and IgA is a dimer. 2. Classes of immunoglobulins and their properties There are five classes of immunoglobulins in humans. 1. Immunoglobulins G are monomers that include four subclasses (IgG1; IgG2; IgG3; IgG4), which differ from each other in amino acid composition and antigenic properties. Antibodies of the IgG1 and IgG4 subclasses specifically bind through Fc fragments to the pathogen (immune opsonization), and due to Fc fragments interact with the Fc receptors of phagocytes, promoting phagocytosis of the pathogen. IgG4 is involved in allergic reactions and is unable to fix complement. Properties of immunoglobulins G: 1) play a fundamental role in humoral immunity in infectious diseases; 2) cross the placenta and form anti-infective immunity in newborns; 3) are able to neutralize bacterial exotoxins, bind complement, participate in the precipitation reaction. 2. Immunoglobulins M include two subclasses: IgM1 and IgM2. Properties of immunoglobulins M: 1) do not cross the placenta; 2) appear in the fetus and participate in anti-infective protection; 3) are able to agglutinate bacteria, neutralize viruses, activate complement; 4) play an important role in the elimination of the pathogen from the bloodstream, activation of phagocytosis; 5) are formed in the early stages of the infectious process; 6) are highly active in the reactions of agglutination, lysis and binding of endotoxins of Gram-negative bacteria. 3. Immunoglobulins A are secretory immunoglobulins that include two subclasses: IgA1 and IgA2. The composition of IgA includes a secretory component consisting of several polypeptides, which increases the resistance of IgA to the action of enzymes. Properties of immunoglobulins A: 1) are found in milk, colostrum, saliva, lacrimal, bronchial and gastrointestinal secretions, bile, urine; 2) participate in local immunity; 3) prevent bacteria from attaching to the mucosa; 4) neutralize enterotoxin, activate phagocytosis and complement. 4. Immunoglobulins E are monomers, the content of which in blood serum is negligible. This class includes the bulk of allergic antibodies - reagins. The level of IgE is significantly increased in people with allergies and infected with helminths. IgE binds to Fc receptors on mast cells and basophils. Properties of immunoglobulins E: upon contact with an allergen, bridges are formed, which is accompanied by the release of biologically active substances that cause immediate allergic reactions. 5. Immunoglobulins D are monomers. They function primarily as membrane receptors for antigen. Plasma cells secreting IgD are localized mainly in the tonsils and adenoid tissue. Properties of immunoglobulins D: 1) participate in the development of local immunity; 2) have antiviral activity; 3) activate complement (in rare cases); 4) participate in the differentiation of B cells, contribute to the development of the anti-idiotypic response; 5) participate in autoimmune processes. LECTURE No. 13. Immunopathology 1. Immunodeficiency states Immunodeficiency states are called violations of the immune status and the ability to a normal immune response to various antigens. These disorders are caused by defects in one or more parts of the immune system. Immunodeficiency states are divided into: 1) congenital (associated with a genetic block in the development of the immune system in ontogenesis, a predetermined violation of the processes of proliferation and differentiation of immunocompetent cells); 2) acquired (arise as a result of violations of immunoregulation associated with past infections, injuries, therapeutic effects, etc.). According to the level of the defect in the immune system, there are: 1) predominant defects in the B-system (syndromes of hypogammaglobulinemia or agammaglobulinemia); 2) predominant defects of the T-system; 3) combined defects of T- and B-systems. The main causes of immunodeficiency states: 1) infections accompanied by the reproduction of the pathogen directly in the cells of the immune system (AIDS virus, infectious mononucleosis). Infected immunocompetent cells can be destroyed under the action of the pathogen itself, its components or waste products (toxins, enzymes), as well as due to a specific immune response of the body directed against microbial agents included in the cell membrane; 2) violation of the processes of immunoregulation during the infection. At the same time, the ratio of regulatory subpopulations of T-helpers and T-suppressors is disturbed; 3) congenital or acquired metabolic and hormonal defects occurring in diseases such as diabetes mellitus, obesity, uremia, malnutrition, etc.; 4) immunoproliferative diseases; 5) the use of immunosuppressive effects and drugs. Immunodeficiency states lead to the emergence of opportunistic infections caused by opportunistic microorganisms, tumors, allergic and autoimmune processes. For infectious diseases that have arisen against the background of immunodeficiency states, the following are characteristic: 1) recurrence of acute infections; 2) protracted, sluggish nature of diseases; 3) a pronounced tendency to generalize the infectious process; 4) high risk of chronic diseases with frequent subsequent exacerbations and steadily progressive course of the pathological process; 5) early, rapid accession of opportunistic microflora; 6) the leading role of mixed infection in the formation of the inflammatory process; 7) unusual pathogens; 8) atypical forms of diseases; 9) severe course of diseases; 10) opportunistic infections; 11) resistance to standard therapy. 2. Allergic reactions. Features of infectious allergy Allergy is a state of increased sensitivity of the body to re-sensitization by antigens. Allergy occurs on the re-introduction of the allergen. The reaction goes through a prolonged immune response and manifests itself after a certain latent period. Allergens are antigens to which an allergic reaction occurs in the body. Allergens can have different origins: 1) household; 2) medicinal; 3) animal origin; 4) vegetable; 5) food; 6) infectious. Any form of allergy is a protective reaction of the body, but it can be pathological in nature, since the elimination of antigens is carried out due to the death of the body's own cells and tissues. Allergies may be based on a humoral and cellular immune response. According to the mechanisms and clinical manifestations, four types of allergies are distinguished. 1. Anaphylactic. Ag-AT complexes are formed, which are fixed on various target cells, mast cells, basophils, sensitizing them to the corresponding allergen. When the allergen enters the body again, allergy mediators are released, which cause the corresponding clinical picture. 2. Cytotoxic. During repeated sensitization, the antigen is adsorbed on the membrane of the corresponding cells, therefore, the antibodies produced are antibodies to tissue antigens as well. The resulting complex AG - AT leads to cytolysis - the death of its own cells. 3. Immunocomplex. With the repeated introduction of the antigen, an excess of the AG-AT complex leads to a powerful activation of complement, it has a damaging effect on the cells of the body's tissues. 4. Cellular. It is based on a cellular immune response. T-killers are responsible for the development of the reaction. Delayed-type hypersensitivity develops. Underlies infectious allergies. An infectious allergen is a weak allergen, the state of allergy develops only in its presence. Infectious allergy develops: 1) in the chronic form of dysentery, gonorrhea, tuberculosis, in the tertiary period of syphilis; in this case, gummas are formed - tumor-like growths of lymphoid tissue; 2) with especially dangerous infections: plague, anthrax, tularemia, brucellosis; 3) with deep mycoses; 4) during the period of convalescence with typhoid and paratyphoid diseases. With a number of infections, an allergological diagnostic method can be used, which consists in setting allergic tests: 1) for tuberculosis - Mantoux test with tuberculin; 2) in the chronic form of dysentery - Tsuverkalov's test with dysentery; 3) in case of gonorrhea - test with gonovaccine; 4) with brucellosis - Burne test with brucellin; 5) with tularemia - a test with tularemine; 6) with anthrax - a test with anthraxin. Positive allergic tests are given by patients, bacterial carriers and those vaccinated with a live vaccine. 3. Autoimmune processes Autoimmune processes are such conditions in which the production of autoantibodies occurs (or the accumulation of a clone of sensitized lymphocytes to the antigens of the body's own tissues). When autoimmune mechanisms cause a violation of the structure and functions of organs and tissues, they speak of autoimmune aggression and autoimmune diseases. The mechanisms of immune tissue damage are similar to immune damage induced by exoallergens - according to the type of delayed and immediate types of hypersensitivity. There are several mechanisms for the formation of autoantibodies. One of them is the formation of autoantibodies against natural, primary antigens of immunologically barrier tissues. There are three mechanisms for inducing an autoimmune response (autosensitization): 1) the formation of autoantigens; 2) the emergence or depression of clones of T- and B-lymphocytes that carry receptors for the determinants of their own tissues (tolerance cancellation); 3) reproduction in the body of microorganisms containing cross-reacting antigens. The production of autoantibodies and the activation of autologous T-lymphocytes do not normally occur due to the innate state of natural immunological tolerance to self antigens, which is formed during embryogenesis. In this case, autoreactive clones of immunocompetent cells, as a result of contact with autoantigens, are eliminated, blocked, or go into a suppressive state. An autoimmune response can develop as a result of immunization with the body's own antigens, to which tolerance has not been developed (or it has been lost). As a result, the immune system, upon contact with autoantigens, reacts with them as if they were foreign. Loss of natural immunological tolerance to certain antigens may be the result of: 1) antigenic stimulation with modified or cross-reacting antigens; 2) violations of immunoregulatory subpopulations of T-lymphocytes. Autoimmunization is possible under the action of cross-reacting antigens, which are found in many bacteria and viruses. When they enter the body, they are recognized by the corresponding clones of T-helper cells, which activate B-lymphocytes to the immune response. This may result in self-aggression. During infections and some destructive processes in the cells of the body, previously hidden antigenic determinants can be exposed (desquamated), against which the autoimmune process begins. Autoimmune processes can occur with primary changes in the immune system - with lymphoproliferative diseases (leukemia). In this case, the reproduction of the "forbidden" clone of lymphocytes occurs. LECTURE № 14. Applied immunology 1. Immunodiagnostics Immunodiagnostics is the use of immune reactions to diagnose infectious and non-infectious diseases. Immunity reactions are the interaction of an antigen with the products of an immune response. In any immune reaction, two phases are distinguished: 1) specific - due to the interaction of the antigen with the antibody and the formation of the AG-AT complex; 2) non-specific. All immune reactions are divided into: 1) simple; two components are involved (antigen and antibody); 2) complex; three or more components are involved (antigen, antibody, complement, etc.). Also distinguish: 1) straight; the result is taken into account visually without special indicator systems; 2) indirect; accounting requires special indication systems. For immunodiagnostics, the following immune reactions are used. 1. An agglutination reaction is the adhesion and precipitation of a corpuscular antigen under the action of an antibody in the presence of an electrolyte. There are the following modifications of the agglutination reaction: 1) passive hemagglutination reaction (RPHA); 2) latex agglutination; 3) co-agglutination; 4) antiglobulin test (Coombs reaction). The most common reaction is RPGA. In it, one of the components (antigen or antibody) is adsorbed on erythrocytes, which, when the AT-AG complex is formed, stick together and precipitate. In latex agglutination, latex particles are used as a sorbent, and in co-agglutination, Staphylococcus aureus cells are used. The Coombs reaction is used to detect incomplete antibodies. 2. The precipitation reaction is the precipitation of an antigen from a solution under the action of an antibody of a precipitating serum in the presence of an electrolyte. A soluble antigen is involved in the reaction. 3. The complement fixation reaction (RCC) is a complex, multicomponent indirect immune response. Includes two systems: 1) the test, consisting of an antigen and an antibody (one of them is unknown), to which a complement is also introduced; 2) indicator, consisting of sheep erythrocytes and hemolytic serum containing antibodies to them. If the antigen and antibody match each other in the system under study, then they form a complement-binding complex. In this case, there will be no changes in the indicator system. If the antigen and antibody do not correspond to each other in the system under study, then the AG-AT complex is not formed, the complement remains free. It binds to the AG-AT complex of the indicator system and thereby causes hemolysis of erythrocytes. 4. Reactions involving labeled antigens or antibodies: 1) radioimmunoassay (RIA); based on the use of radioiodine-labeled or hydrogen-labeled antibodies. The resulting complex AG - AT with a radioactive label is detected using radiometers; 2) immunofluorescence reaction; is based on the fact that the antibodies of the immune serum are labeled with fluorochromes. The AG-AT complex is detected by fluorescence microscopy; 3) enzyme immunoassay (ELISA); the reaction component is labeled with an enzyme, which, if positive, is included in the AG-AT complex. When an appropriate substrate is added, a color change occurs. 5. Toxin neutralization reaction (to determine the type of pathogen toxin). A mixture of toxin and antitoxic serum is injected into white mice, and if they match, i.e., are neutralized, the mice do not die. 2. Immunoprophylaxis Immunoprophylaxis is the use of immunological patterns to create artificial acquired immunity (active or passive). For immunoprophylaxis use: 1) antibody preparations (vaccines, toxoids), upon administration of which artificial active immunity is formed in a person; 2) antibody preparations (immune sera), with the help of which artificial passive immunity is created. Vaccines are called antigenic preparations derived from pathogens or their structural analogues, which are used to create artificial active acquired immunity. According to the method of preparation, they distinguish: 1) live vaccines. Prepared from avirulent strains of the pathogen. In fact, they reproduce in the human body an easily occurring infection, but not an infectious disease, during which the same defense mechanisms are formed and activated as in the development of infectious immunity. They create intense and long-lasting immunity; 2) killed vaccines. They are prepared from microorganisms inactivated by heating, UV rays, chemicals, under conditions that exclude the denaturation of antigens; 3) chemical vaccines. They contain chemically pure antigens of pathogens. Possess weak immunogenicity; 4) genetically engineered vaccines. Developed in virology, with the creation of hybrid vaccine strains. The genes responsible for its main antigenic markers are introduced into the genome of a known vaccine strain; 5) combined vaccines. They are preparations consisting of a microbial antigenic component and synthetic polyions - powerful stimulators of the immune response; 6) associated vaccines. They are a complex of killed vaccine and toxoid. Anatoxins are antigenic preparations obtained from exotoxins during their sterilization treatment. At the same time, the toxoid is devoid of the toxicity of the original exotoxin, but retains its antigenic properties. With the introduction of toxoids, antitoxic immunity is formed, since they induce the synthesis of antitoxic antibodies - antitoxins. Passive immunoprophylaxis is carried out as an emergency prophylaxis for contact persons when it is necessary to quickly create passive artificial immunity. It is carried out with ready-made antibody preparations - antimicrobial and antitoxic immune sera. Antibacterial sera contain antibodies to bacterial cellular antigens. Antitoxic sera contain antibodies to protein exotoxins. They are obtained by immunizing horses with toxoids. These sera are introduced into the human body fractionally according to the Bezredk method in order to avoid anaphylactic shock. The unit of action of antitoxic serum is 1 IU. 1 IU is the minimum amount of antitoxic serum that can neutralize 100 lethal doses of the corresponding exotoxin. 3. Immunotherapy Immunotherapy is the use of immunological patterns to treat patients. The goal of immunotherapy is to enhance specific defense mechanisms against microbial agents. Immunotherapy can be used in chronic sluggish diseases. At the same time, antigenic preparations are introduced to stimulate the protective properties of the body - therapeutic vaccines (always killed). Autovaccines are used for immunotherapy of chronic forms of infections. They are prepared directly from pathogens isolated from a given patient. These are killed vaccines. Autovaccines have an advantage: they induce an immune response in the macroorganism to the antigens of a specific pathogen, taking into account its strain characteristics. In the treatment of acute severe generalized forms of infectious diseases, it becomes necessary to urgently create passive artificial acquired immunity. For these purposes, antibody preparations are used - antitoxic and antibacterial immune sera, immunoglobulins, plasma. The introduction of antitoxic sera is effective only before the adsorption of the toxin by the cells of the body, so their treatment should be started as early as possible. Immunoglobulin preparations are obtained from normal or immune serum and human blood plasma. Immunocorrection is a modern trend in the treatment of infectious and non-infectious diseases. For this use: 1) immunosuppressants (suppress immunity); 2) immunostimulants (stimulate the immune system); 3) immunomodulators (they can have a multidirectional effect on the immune system, depending on its initial state). These drugs may be: 1) exogenous origin; 2) endogenous origin; 3) synthetic. Preparations of exogenous (microbial) origin are most often used for chronic infections, prolonged non-healing of wounds. They stimulate the immune system. They are obtained from the components of bacteria - lipopolysaccharides and peptidoglycans of the cell wall. Preparations: pyrogenal, ribomunim, sodium nucleinate. Preparations of exogenous origin are immunoregulatory peptides. Can be: 1) thymus origin (T-activin, thymalin); used for lesions of the thymus and T-system, allergic conditions; 2) bone marrow origin (myelopeptides); used for lesions of the B-system. For the treatment of viral infections, tumor processes, leukopenia, interferon is used. Synthetic drugs are functional analogues of drugs of endogenous (licopid) and exogenous origin (timogen), immunomodulators (macadine, levomisole). LECTURE No. 15. The causative agents of intestinal infections - the family of enterobacteria 1. Characteristics of the Enterobacteriaceae family The Enterobacteriaceae family includes numerous representatives that share a common habitat - the intestines. Enterobacteria are divided into: 1) pathogenic (shigella, salmonella, escherichia, yersinia, etc.); 2) conditionally pathogenic (37 genera). All pathogenic enterobacteria can cause acute intestinal infections in humans, opportunistic pathogens - purulent-inflammatory diseases and food poisoning. Enterobacteria are gram-negative rods of medium size with rounded ends, arranged randomly. Some of them are mobile due to flagella, others are immobile. They are facultative anaerobes. They are undemanding to nutrient media. Colonies of the same type are formed on meat-peptone agar. Medium size, round, smooth, convex, shiny, colorless. They grow in meat-peptone broth, giving a uniform turbidity. Biochemical tests are common to the entire family. Based on these tests, the Enterobacteriaceae family is differentiated from others that are similar in morphology. All enterobacteria: 1) ferment glucose to acid or to acid and gas; 2) reduce nitrates to nitrites; 3) catalase +, oxidase -, OF-test ++. Enterobacteria antigens consist of: 1) O-antigen, which is localized in the cell wall. By chemical nature, it is a glucidolipoid complex; 2) K-antigen (this is a surface, capsular antigen); 3) H-antigen (thermolabile, flagellar); motile enterobacteria have it; 4) pilifimbrial antigen; it is present in bacteria that have villi, pili, fimbriae. Enterobacteria classification The classification of enterobacteria is based on their biochemical properties. According to Bergey's classification, the family of Enterobacteria is divided into 40 genera, genera - into species. In some cases, intraspecific differentiation into: 1) fermenters; 2) serogroups and serovars; 3) fagovars; 4) ringworms. This differentiation is necessary for epidemiological analysis, i.e., to establish the source and ways of spreading the infection. Intestinal infection is the result of the interaction of the pathogen with the corresponding structures of the macroorganism under the necessary environmental conditions. This process consists of several phases: 1) adhesion; 2) invasions; 3) colonization; 4) production of exo- and enterotoxins. Adhesion is a prerequisite for the occurrence of any infectious process. Different enterobacteria have tropism only for certain epithelial cells, therefore, they attach only at a certain level of the gastrointestinal tract. Adhesion occurs in two stages: 1) non-specific adhesion (approximation); 2) specific adhesion (as a result of ligand-specific interaction of the corresponding structures of enterobacteria (villi, fimbriae) and receptors of the plasmolemma of epithelial cells). Invasion - the penetration of bacteria into epithelial cells with or without reproduction. Invasion, colonization and production of toxins are expressed to varying degrees in different enterobacteria, so the pathogenesis and clinic of intestinal infections differ significantly. 2. Escherichia The genus Escherihia includes seven species. The most important species is E. coli, which are divided by pathogenicity into: 1) pathogenic (diarrheal); 2) conditionally pathogenic (they are part of the normal intestinal microflora). They are mobile, do not form capsules. Biochemical properties: 1) ferment glucose with the formation of acid and gas; 2) ferment lactate. Antigenic structure: 1) according to the O-antigen, they are divided into serogroups (more than 160); 2) the majority have K-AG and N-AG. Diseases caused by Escherichia are divided into two groups: 1) endogenous co-infections; are caused by their own Escherichia coli, which, with a decrease in immunological reactivity, causes purulent-inflammatory diseases; 2) exogenous coli infections - escherichiosis. These are typical intestinal infections, caused only by pathogenic E. coli that enter the body from outside. The main source is man. Pathogenic E. coli are divided into four main classes. 1. ETEC - enterotoxigenic Escherichia coli. They have a tropism for the epithelium of the small intestine. Once in the body, they attach to the receptors of enterocyte membranes. They have the SF factor of colonization, due to which they populate the epithelial cells of the small intestine. They do not penetrate inside the cells, and inflammation does not develop. They produce exoenterotoxin, the synthesis of which is encoded by the plasmid. This toxin is made up of: 1) LT-thermolabile fraction; 2) ST-thermostable fraction. The toxin has a cytotonic effect. As a result of its impact, the process of enterosorption is disrupted, which leads to the development of diarrheal syndrome. Clinically, the disease proceeds as a mild form of cholera. 2. EIEC - enteroinvasive coli. They have a tropism for the epithelial cells of the large intestine. The factors of their virulence are the presence of outer membrane proteins on the surface of the cell wall, the ability to invade and intracellular reproduction. Bacterial reproduction leads to cell death. In place of dead cells, ulcers and erosion are formed, surrounded by inflammation. 3. EPEC - enteropathogenic Escherichia coli. Cause enterocolitis in children under one year old. The epithelium of the small intestine is affected. Virulence factor - the ability to limited invasion. 4. EHEC - enterohemorrhagic Escherichia coli. They have a tropism for the epithelial cells of the large intestine. The virulence factor is the production of two types of Shigo-like toxins (SLTs). Cause hemocolitis. The main diagnostic method is bacteriological examination. It is necessary to determine: 1) belonging of the isolated E. coli culture to the pathogenic serogroup (agglutination and precipitation reactions); 2) the presence of a toxin (using enzyme-linked immunosorbent assay (ELISA)), if the isolated structure belongs to the ETEC serogroup; 3) the presence of outer membrane proteins (ELISA), if the isolated structure belongs to the EIEC serogroup; 4) a special protein substance common to the whole group (ELISA) - in the EPEC group; 5) the presence of SLT (ELISA) - from ENEC. There is no specific prevention. Treatment: antibiotics. 3. Shigella They belong to the genus Shigella. They are the causative agents of dysentery. The morphology is the same as that of other members of the Enterobacteriaceae family. They are immobile and do not form capsules. They grow well on simple nutrient media. Colorless colonies form on Endo's medium. The genus includes four species that differ in biochemical properties (the ability to ferment mannitol and lactose) and antigenic structure: 1) Sh. disenteriae; do not ferment lactose and mannitol; according to antigenic properties within the species are divided into 12 serovars; one of them - shigella Grigorieva-Shiga - the most pathogenic; 2) Sh. flexneri; only ferments mannitol; according to antigenic properties, it is divided into 6 serovars, which are divided into subserovars; 3) Sh. boydii; only ferments mannitol; according to the antigenic structure, it is divided into 18 serovars; 4) Sh. sonnei; ferments only lactose; antigenically, the species is homogeneous; fermentovars, fagovars, and koletsinovars are distinguished within the species. Shigella, bypassing the stomach and small intestine, enter the large intestine. They attach to colonocyte membrane receptors and penetrate through the outer membrane protein. Cell death leads to the formation of erosions and ulcers surrounded by perifocal inflammation. Pathogenic factors: 1) proteins of the outer membrane (provide the ability for invasion and intracellular reproduction); 2) contact hemolysin (promotes lysis of cell vacuole membranes); 3) exotoxin (has enterotropic, cyto- and neurotoxic effects); 4) endotoxin (has a general toxic effect on the body and protects the Shigella that have entered the body from the action of the protective forces of the macroorganism). There are three clinical forms of dysentery, which differ in pathogens, epidemiology and partly in the clinic: 1) Grigoriev-Shiga dysentery. Pathogen - Sh. disenteriae, serovar - Shigella Grigorieva-Shiga. Ways of transmission - alimentary, contact-household. Features of the clinic: it is difficult, bloody diarrhea with blood is characteristic, symptoms of CNS damage, there may be bacteremia; 2) Flexner's dysentery. Pathogens - Sh. flexneri and Sh. boydii. Water transmission route. Features of the clinic: proceeds as a typical dysentery of varying severity; 3) Sonnei dysentery. food transmission route. Features of the clinic: there may be symptoms of food poisoning, vomiting. Diagnostics: 1) bacteriological examination; 2) immunoindication (ELISA); 3) serodiagnosis (has a retrospective value). Specific prophylaxis: dysenteric bacteriophage (used in foci of infection). Etiotropic therapy: in the moderate and severe degree of the disease, antibiotics are prescribed (those that are excreted by the intestines), taking into account the sensitivity of the pathogen. 4. Salmonella The genus Salmonella includes more than 2500 serovars. Morphology is similar to other members of the family. The bacteria are motile and do not form spores or capsules. They grow well on simple nutrient media. They form small transparent colonies. Biochemical properties: 1) ferment carbohydrates to acid and gas; 2) lactose is not decomposed; 3) deaminate and decarboxylate some amino acids. According to biochemical differences, the genus is divided into six groups. Antigenic structure: 1) O-antigen. According to its structure, Salmonella are divided into 65 serogroups; 2) H-antigen. According to its structure, Salmonella serogroups are divided into serovars within the serogroup. In humans, salmonella can cause two groups of diseases: 1) anthroponotic - typhoid fever and paratyphoid A and B; pathogens: S. typhi, S. paratyphi A, S. paratyphi B; 2) zooanthroponic - salmonellosis; pathogens: S. typhimurium, S. haifa, S. anatum, S. panama, S. infantis. Typhoid fever and paratyphoid fever A and B are combined into one group - typhoid and paratyphoid diseases - due to a common pathogen, clinic, pathogenesis. The source of infection is a patient (or a bacteriocarrier). The disease includes five phases. 1. The phase of the introduction of the pathogen into the body, its attachment to the receptors of enterocyte membranes and penetration into the cells (corresponding to the incubation period of the disease). 2. Phase of primary localization: Salmonella penetrate into the lymphatic apparatus of the small intestine, sensitize it, multiply in macrophages; this is accompanied by the death of microorganisms and the release of endotoxin, which enters the bloodstream and causes endotoxemia (corresponding to the prodromal period). 3. Bacteremia phase: the pathogen breaks through the lymphatic barrier and enters the bloodstream, spreading to all parenchymal organs (the onset of the disease). 4. Phase of secondary localization: typhoid granulomas appear in the parenchymal organs (the height of the disease). 5. The excretory-allergic phase: repeated contact of the pathogen with the primary sensitized lymphatic apparatus of the small intestine; ulcers form on the mucous membrane. The outcome of the disease can be different: 1) recovery; 2) formation of carriage; 3) lethal. Diagnosis of typhoid and paratyphoid diseases: 1) in the phase of bacteremia - blood for hemoculture (RPHA), if there is a rash - scraping with roseol; 2) in the phase of convalescence - bacteriological examination of feces, urine, bile; 3) to identify carriage - a serological study. Etiotropic therapy: antibiotics, taking into account the sensitivity of the pathogen. Specific prophylaxis: killed typhoid vaccine. The second group of diseases - salmonellosis - is characterized by a variety of clinical manifestations. Sources of infection - sick animals, infected food. The route of infection is alimentary. Most often, salmonellosis occurs as a food poisoning. In this case, Salmonella affects the enterocytes of the small intestine and is fixed in its lymphatic apparatus. When the lymphatic barrier is broken, bacteremia develops, the pathogen spreads to various organs, and extraintestinal forms of salmonellosis are recorded. 5. Yersinia The genus Yersinia contains seven species, of which Y. pestis (the causative agent of plague), Y. pseudotuberculesis (the causative agent of pseudotuberculosis), Y. enterocolitica, the causative agent of acute intestinal infections, intestinal yersiniosis, are pathogenic for humans. Y. enterocolitica are gram-negative, motile rods that do not form spores or capsules. Cultivated on simple nutrient media at a temperature of 20-26 °C. Biochemical properties: 1) ferment sorbose, inositol with the formation of acid; 2) form urease. By specificity, O-antigens are divided into 30 serovars. Most often, the disease is caused by the O3 and O9 serovars. Yersinia are resistant and capable of reproduction in the external environment, withstand low temperatures. Able to multiply in milk, vegetables, fruits, ice cream at low temperatures. In open waters, they survive and reproduce. Yersiniosis is a zooanthroponotic disease. Reservoir - various rodents that excrete bacteria in feces and urine. The route of infection is alimentary. Diseases are recorded in the form of outbreaks or sporadic cases. Y. enterocolitica are facultative intracellular parasites. The pathogenicity of Yersinia is associated with invasive properties and the action of cytokines; virulent strains are resistant to phagocytosis and the bactericidal action of serum. These properties encode the plasmid genes. Virulence markers are calcium dependence and autoagglutination. Infection can be realized in different ways: from asymptomatic carriage and mild forms to severe and generalized, septic (more often in the elderly, suffering from chronic diseases). There are four phases in pathogenesis. 1. Implementation. Yersinia have a tropism for the epithelial cells of the small intestine, penetrate into the lymphatic apparatus. 2. Enteral. Reproduction is accompanied by the death of microorganisms, the release of endotoxin. It is clinically expressed by the phenomena of enterocolitis and lymphadenitis. At this stage, the process may end, then a typical intestinal infection develops. If there is a breakthrough of the lymphatic barrier, then the third phase follows. 3. Bacteremia: sepsis and scarlet fever develop. 4. Secondary focal and allergic manifestations. Hepatitis, arthritis, urticaria are registered. Any organ can be affected. Diagnostics: 1) bacteriological examination; material - feces, blood, urine; sowing on Serov's medium; crops are cold enriched for a week; 2) serological examination (RPGA); 3) immunoindication. Specific prophylaxis is not carried out. Etiotropic therapy: 1) antibiotics; 2) sulfonamides. LECTURE No. 16. Food poisoning. Food toxicosis 1. General characteristics and causative agents of PTI Food poisoning (FTI) is a large group of acute intestinal infections that develop after eating foods contaminated with pathogens and their toxins. Clinically, these diseases are characterized by a sudden onset, a combination of intoxication syndromes, gastroenteritis, and the frequent development of dehydration. Food poisoning can be caused by: 1) salmonella; 2) shigella; 3) conditionally pathogenic microorganisms (P. vulgaris, P. mirabilis, enterococci); 4) enterotoxic strains of staphylococcus (St. aureus St. albus); 5) streptococci (beta-hemolytic streptococci of group A); 6) spore anaerobes (Clostridium perfringens); 7) spore aerobes (Bac. cereus); 8) halophilic vibrios (Vibrio parahaemolyticus), etc. Most often they are caused by salmonella and opportunistic pathogens that are widespread in the environment. Most of them live in the intestines of healthy people in the form of saprophytes. For the development of the disease requires a number of contributing factors: 1) a sufficient dose of the pathogen; 2) appropriate virulence and toxigenicity; 3) reduced resistance of the macroorganism; 4) the presence of concomitant diseases, etc. PTI pathogens are capable of producing toxins both in food products and in the human body. With the destruction of pathogens in the gastrointestinal tract, additional portions of various kinds of toxic substances are formed. The body responds to a massive ingestion of pathogens and toxic products into the human gastrointestinal tract with a stereotyped reaction. The action of the complex of toxins causes local changes in the gastrointestinal tract (inflammatory process, perversion of motility), general toxic syndrome (headache, hyperthermia, disruption of the cardiovascular and nervous systems, etc.). In general, this group of diseases is characterized by a short incubation period, acute onset and rapid development, a combination of signs of damage to the gastrointestinal tract and severe intoxication. There are some features of the clinical picture, depending on the type of pathogen: 1) Salmonella PTI are characterized by a severe course, epidemic outbreaks are possible; 2) with staphylococcal etiology, the disease develops most acutely after a very short incubation period (30-60 minutes); begins with the appearance of nausea, vomiting, there is a strong cutting pain in the abdomen, resembling gastric colic; 3) with clostridial etiology, PTI develops rapidly, starting with the appearance of intense, stabbing abdominal pain, accompanied by nausea, vomiting and loose bloody stools at normal body temperature; 4) PTI of proteic etiology is characterized by a sharp fetid odor of feces. Diagnostics: 1) bacteriological examination of excretions of patients, food products; 2) serodiagnosis. 2. Botulism The causative agent of botulism belongs to the genus Clistridium, species Cl. botulinum. It is the causative agent of food poisoning. Food toxicosis is a disease that occurs when eating food containing exotoxins of the pathogen, while the pathogen itself does not play a decisive role in the development of the disease. Cl. botulinum are Gram-positive large rods. They form subterminally located spores. Capsules do not. Strict anaerobes. They multiply on blood-glucose agar, forming irregularly shaped colonies with processes or smooth edges, a zone of hemolysis around the colonies. When growing in an agar column, they resemble cotton balls or lentils. In liquid media, a uniform turbidity is formed, and then a compact precipitate falls to the bottom of the test tube. The natural habitat of Clostridium botulism is the intestines of fish, animals, microorganisms enter the soil with feces. Able to persist and multiply in the external environment for a long time in the form of spore forms. Vegetative forms are unstable in the external environment. The enzymatic activity is unstable and is not used for identification. According to the antigenic structure of the produced toxins, serovars A, B, C1, D, E, F, Q are distinguished. The antigenic specificity of the bacteria themselves is not determined. Clostridium botulism produces the most powerful of the exotoxins - botulinum. Botulinum toxin accumulates in the food product, multiplying in it. Such products are usually home-made canned food, raw smoked sausages, etc. The toxin has a neurotropic effect. With the development of the disease, toxinemia always occurs, the medulla oblongata and nuclei of the cranial nerves are affected. The toxin is resistant to the action of digestive enzymes, it is quickly absorbed from the upper digestive tract into the blood and enters the neuromuscular synapses. Botulinum toxin binds to the synaptosome membrane and enters the nerve cell by endocytosis. The mechanism of action of the toxin is the inhibition of calcium-dependent release of acetylcholine, the blockade of the functional activity of the neuron. First of all, the bulbar nerve centers are affected. There are general intoxication, signs of damage to the organ of vision - double vision, accommodation disorder, dilated pupils, damage to the oculomotor muscles. At the same time, swallowing becomes difficult, aphonia, headache, dizziness, and vomiting appear. The disease has a high mortality rate. Diagnostics: 1) infection of laboratory mice; material - vomit, gastric lavage, feces, blood; 2) detection of the toxin in the toxin neutralization reaction; 3) serodiagnosis. Treatment: antitoxic anti-botulinum serum. LECTURE No. 17. Causative agents of zooanthroponic infections 1. Plague The causative agent of the plague belongs to the genus Yersinia, species Y. pestis. These are gram-negative polymorphic small rods with rounded ends. They are motionless. Dispute does not form. In the patient's body and during reproduction on nutrient media, they form a capsule. Methylene blue-stained smears show bipolarity. They are facultative anaerobes. They multiply on simple nutrient media, but it is better when hemolyzed blood is added. The optimum temperature for cultivation is 28 °C. Yersinia plague tolerates low temperatures well and can remain viable for a long time in the environment and in humans and animals. Sensitive to UV radiation, drying, high temperatures. Biochemical activity: they break down carbohydrates with the formation of acid, weak proteolytic activity - gelatin is not diluted, milk is not coagulated. Plague wand antigens: 1) O-antigen (somatic, localized in the cell wall); 2) F-antigen (surface protein thermostable antigen); 3) V- and W-antigens (have antiphagocytic activity). Pathogenic factors: 1) the presence of antigens with antiphagocytic activity; 2) the formation of pesticides; 3) the ability to assimilate hemin and synthesize purines; 4) the ability to produce a toxin ("mouse poison" - blocks the action of a number of metabolites and hormones). The main hosts of Yersinia plague in nature are rodents (ground squirrels, tarbagans, etc.). Infection of a person occurs transmissible (carriers - fleas), contact and alimentary routes. Patients with the pneumonic form of plague infect others by aerogenic means. The clinical manifestations of plague depend on the entrance gate of infection. There are the following forms of the disease: 1) skin-bubonic; 2) primary pulmonary; 3) secondary pulmonary; 4) primary septic; 5) secondary septic. The main breeding site of the pathogen is the lymph nodes. Insufficient barrier function of the lymph nodes leads to the development of the primary septic form of plague. The secondary septic form develops against the background of bubonic or pulmonary forms. After the illness, a strong long-term immunity remains. Plague is a particularly dangerous infection. Work with materials containing the pathogen is carried out in special laboratories, trained by personnel, subject to established safety measures. Diagnostics: 1) bacteriological research. Materials - pus from buboes, ulcer discharge, sputum. Crops are subjected to cold enrichment; 2) serodiagnosis - RPHA; 3) immunoindication reactions. Treatment: antibiotic therapy is carried out with streptomycin, anti-plague immunoglobulin. Specific prophylaxis: live or chemical plague vaccine; creates a strong immunity for 6 months. 2. Anthrax The causative agent belongs to the genus Bacillus, species B. anthracis. They are Gram-positive, large, non-motile rods. Outside the body, in the presence of oxygen, they form spores located centrally. Spore forms are particularly persistent in the external environment. In the body and on nutrient media form a capsule. In smears are arranged in chains. The causative agent is an aerobe or a facultative anaerobe. It reproduces well on simple nutrient media. On the surface of the agar forms rough colonies with jagged edges. Growth in the broth is characterized by the appearance of white flakes that settle to the bottom of the tube. On nutrient agar with penicillin, the transformation of bacteria into protoplasts in the form of separate balls arranged in a chain is observed - the "pearl necklace" phenomenon. Biochemically highly active: 1) liquefy gelatin; 2) break down carbohydrates; 3) restore nitrates; 4) hydrolyze starch, casein. Antigens of anthrax bacilli: 1) a specific capsular antigen of a protein nature; 2) group somatic antigen of polysaccharide nature; localized in the cell wall, thermostable. pathogenicity factors. 1. Toxin, consisting of three components: 1) edematous factor causing dermonecrotic reaction; 2) lethal toxin causing pulmonary edema and severe hypoxia; 3) protective antigen. 2. Capsule; has antiphagocytic activity; non-capsular cultures are non-virulent. Under natural conditions, anthrax affects animals: large and small cattle, horses, pigs, deer, camels. The pathological process develops in the intestine. A person becomes infected from sick animals through direct contact, through infected objects, products from contaminated raw materials, meat of sick animals. Transmissible transmission is possible. Clinical forms of the disease: 1) skin - the formation of a carbuncle; 2) intestinal - severe intoxication, vomiting, nausea, diarrhea with blood; 3) pulmonary - severe bronchopneumonia. In those who have been ill, a strong immunity is created. During the course of the disease, a specific sensitization is created. Diagnostics: 1) bacteriological examination; the material for the study is determined by the clinical form of the disease; 2) allergic test with anthraxin; a positive reaction is determined from the first days of the disease and persists for many years after recovery; 3) serodiagnosis - thermoprecipitation according to Aksoli. Treatment: 1) anti-anthrax immunoglobulin; 2) antibiotics (penicillin, streptomycin). Specific prevention: 1) live anthrax vaccine; creates immunity for a year; 2) emergency prophylaxis - anti-anthrax immunoglobulin. 3. Tularemia The causative agent of tularemia belongs to the genus Francisella, the species F. tularensis. These are very small polymorphic, coccoid or rod-shaped gram-negative bacteria. Dispute does not form. They do not have flagella. Form a small capsule. facultative anaerobes. They do not grow on simple nutrient media. Reproduction requires the introduction of cysteine into the medium. Growth is possible on media containing egg yolk, on blood agar with the addition of glucose and cysteine. On dense media form small whitish colonies. In the environment, the pathogen remains viable for a long time. Not resistant to high temperatures. Biochemical properties are unstable, enzymatic activity is poorly expressed. They produce hydrogen sulfide. Antigens - O-antigen; somatic, localized in the cell wall, induces the synthesis of agglutinins and precipitins. The pathogenicity factor is endotoxin. The natural hosts of the pathogen are rodents (water rats, voles, house mice, hamsters, hares). Human infection occurs through direct contact with sick animals or dead bodies, through contaminated water and food. Carriers of the disease can be ticks, mosquitoes, horseflies. The pathogen enters the human body through the skin and mucous membranes of the eyes, mouth, nose, respiratory tract and digestive tract. Then the pathogen is in the lymphatic tract, where it multiplies intensively and appears in the blood. Clinical forms of tularemia: 1) bubonic; 2) anginal-bubonic; 3) intestinal; 4) pulmonary; 5) primary septic. It is accompanied by the development of a specific allergic reaction that occurs on the 3-5th day of the disease and persists after recovery for many years. After the illness, a stable, long-term immunity remains. Diagnostics: 1) serodiagnosis; from the 2nd week of the disease, antibodies are determined in the blood serum in agglutination and RNHA reactions; with repeated studies, an increase in antibody titer is observed; 2) infection with the test material (bubo punctate, nipples, ulcers, conjunctival discharge, throat plaque, sputum, blood) of white mice or guinea pigs; smears are made from the organs of animals and sowing on a folded yolk medium; 3) thermoprecipitation reaction; 4) staging an allergic test with turyarin; the test becomes positive from the 3-5th day of the disease. Treatment: antibiotics are used - streptomycin, tetracycline, chloramphenicol. Specific prophylaxis: Gaisky-Elbert live vaccine; immunity is created for 5-6 years. 4. Brucellosis The causative agent belongs to the genus Brucella. There are three types of pathogens for humans: 1) B. melitensis; 2) B. abortus; 3) B. suis. These are small Gram-negative coccobacilli. They do not have flagella. Dispute does not form. Freshly isolated strains can form a delicate capsule. Brucella are demanding on nutrient media. Use special media with the addition of blood serum, glucose, thiamine, biotin. Growth is very slow. On dense nutrient media, they form small, convex, colorless colonies with a pearly sheen. In liquid media form a uniform turbidity. Under the influence of antibiotics, they pass into L-forms. They are strict aerobes. They are highly resistant to environmental factors, retain their viability for a long time at low temperatures, and are highly sensitive to high temperatures and disinfectants. Biochemical properties of brucella: 1) break down glucose and some other carbohydrates; 2) decompose urea and asparagine; 3) hydrolyze protein, peptones, amino acids; 4) have enzymes such as catalase, hyaluronidase, peroxidase, lipase, phosphatase. Brucella antigens: 1) Vi-antigen (surface); 2) somatic species-specific antigens A and B. In B. melitensis, M antigens predominate, while in B. abortus and B. suis, A antigens predominate. Pathogenic factors: 1) endotoxin; 2) enzymes of aggression and defense: hyaluronidase, neuraminidase, etc.; 3) the ability to multiply in the cells of the lymphoid-macrophage system. The natural hosts of the pathogen are different depending on the species: B. melitensis causes the disease in small cattle, B. abortus in cattle, B. suis in pigs. A person becomes infected by contact, alimentary and airborne droplets. More often, the disease is of a professional nature - livestock breeders, workers of meat processing plants, livestock specialists, veterinarians, etc. are sick. The pathogen is able to enter the body through intact mucous membranes. After penetration, it spreads through the lymphogenous route, enters the bloodstream, and then into the spleen, bone marrow, and lymph nodes, where it is localized intracellularly. Can be stored in the body for a long time. From the first days of the disease, a delayed-type hypersensitivity reaction occurs, which persists for a long time after recovery. Diagnostics: 1) bacteriological examination; material - blood, feces, urine; 2) serological examination - Wright agglutination reaction, RSK, RNGA. Incomplete antibodies are detected in the Coombs reaction. Treatment: antibiotics are used (streptomycin, erythromycin, chloramphenicol, etc.). Specific prophylaxis: Live brucellosis vaccine is rarely used. LECTURE No. 18. Pathogenic cocci 1. Staphylococci Family Staphilococcoceae, genus Staphilicoccus. They are the causative agents of staphylococcal pneumonia, neonatal staphylococcus, sepsis, pemphigus. These are small Gram-positive cocci. In smears, they are arranged in clusters, often cluster-shaped. They do not form a dispute, they are motionless. They form microcapsules. They are facultative anaerobes. They are undemanding to nutrient media, grow well on simple media, give pigment colonies. The elective medium for staphylococci is yolk-salt agar, less often milk-salt agar. Staphylococci are resistant to high concentrations of sodium chloride. Unlike micrococci, staphylococci are able to decompose glucose under anaerobic conditions, glycerol - under aerobic conditions. They are sensitive to lysostaphin, since their cell wall contains special teichoic acids - ribitol-teichoic acids. Staphylococci are active biochemically, have proteolytic and saccharolytic activity. According to biochemical properties are divided into types: 1) St. aureus (has many pathogenicity factors, may have a variety of localization of lesions); 2) St. epidermidis (affects the skin); 3) St. saprophiticus (genitourinary tract parasite). Three tests are used to differentiate these three species: 1) fermentation of mannitol under anaerobic conditions; 2) plasmacoagulase production; 3) sensitivity to the antibiotic novobiocin. For St. aureus all three tests are positive, for St. saprophiticus all three tests are negative, St. epidermidis is sensitive to novobiocin. Staphylococcal antigens are divided into: 1) extracellular (variant-specific proteins of exotoxins and exoenzymes); 2) cellular: a) surface (glycoproteins) - variant-specific; b) deep (teichoic acids) - group-specific. Factors of pathogenicity of staphylococci. 1. The role of adhesins is performed by complexes of surface proteins of the cell wall with teichoic acids. 2. Hyaluronidase - a factor of tissue invasion into the intercellular spaces of cells. 3. Enzymes of aggression: 1) plasmacoagulase; 2) fibrinolysin; 3) lecithinase; 4) phosphatases; 5) phosphotidase; 6) exonucleases; 7) proteases. 4. Toxins: 1) hematolysins (a, b, g, d, e); cause hemolysis of human erythrocytes, have a dermatonecrotic effect; 2) hemotoxins; responsible for the development of toxic shock; 3) leukocidin; consists of two fractions; for one, the targets are macrophages, for the other, polymorphonuclear leukocytes; 4) exofoliative exotoxin; causes multiple skin lesions; 5) enterotoxins (A, B, C, D, E); in the alimentary route of infection, they cause food toxicosis or food toxic infections in children, damage enterocytes. Diagnostics: 1) bacteriological research. Wednesday - blood, yolk-salt agar; 2) serodiagnosis. Antibodies to a-hemotoxin are detected in the toxin neutralization reaction. Treatment. 1. Chemotherapy - antibiotics, sulfonamides, nitrofurans. 2. Phage therapy - polyvalent phages. 3. Immunotherapy: 1) staphylococcal toxoids; 2) therapeutic autovaccines; 3) finished antibody preparations. Specific prevention: staphylococcal toxoid (active). 2. Streptococci They belong to the family Streptococcaceae, genus Streptococcus. These are gram-positive cocci, arranged in chains or in pairs in smears. They are facultative anaerobes. Do not grow on nutrient media. On blood agar, small-dotted, pigmentless colonies are produced, surrounded by a zone of hemolysis: a - green, b - transparent. The disease is often caused by b-hemolytic streptococcus. In sugar broth, near-wall growth is given, and the broth itself remains transparent. Grow at 37°C. Streptococci are able to break down amino acids, proteins, carbohydrates. According to biochemical properties, 21 species are distinguished. Most of them are conditionally pathogenic. The most important in the development of infectious diseases are: 1) S. pyogenus, the causative agent of a specific streptococcal infection; 2) S. pneumonia, the causative agent of pneumonia, can cause a creeping corneal ulcer, otitis, sepsis; 3) S. agalactia, may be part of the normal microflora of the vagina; infection of newborns leads to the development of sepsis and meningitis in them; 4) S. salivarius, S. mutans, S. mitis, are part of the normal microflora of the oral cavity; in oral dysbiosis are the leading factors in the development of caries. streptococcal antigens. 1. Extracellular - proteins and exoenzymes. These are variant-specific antigens. 2. Cellular: 1) surface proteins are represented by surface proteins of the cell wall, and in S. pneumonia - by capsule proteins. They are variant-specific; 2) deep - teichoic acids, peptidoglycan components, polysaccharides. They are group specific. pathogenicity factors. 1. Complexes of teichoic acids with surface proteins (play the role of adhesins). 2. M-protein (possesses antiphagocytic activity). This is a superantigen, that is, it causes polyclonal activation of immune system cells. 3. OF-protein - an enzyme that causes hydrolysis of blood serum lipoproteins, reducing its bactericidal properties. The OF protein is important for adhesion. According to the presence or absence of this protein, there are: 1) OF+ strains (rheumatogenic); the entrance gate is the pharynx; 2) OF-strains (nephritogenic); primary adhesion to the skin. 4. Enzymes of aggression and defense: 1) hyaluronidase; 2) streptokinase; 3) streptodornasis; 4) proteases; 5) peptidases. 5. Exotoxins: 1) hemolysins: a) O-streptolysin (has a cardiotoxic effect, a strong immunogen); b) S-streptolysin (weak immunogen, does not have a cardiotoxic effect); 2) erythrogenin (has a pyrogenic effect, causes capillary paresis, thrombocytolysis, is an allergen, occurs in strains that cause complicated forms of infection, in pathogens of scarlet fever, erysipelas). Treatment: 1) etiotropic antibiotic therapy; 2) UV therapy. There is no specific prevention. 3. Meningococci They belong to the genus Neisseria, genus N. meningitidis. These are bean-shaped diplococci, in smears they look like coffee beans. They do not form spores, they do not have flagella, they form a capsule in the body. Gram negative. Strict aerobes. Meningococci are demanding on nutrient media - they grow only on media containing human protein (serum agar, ascites agar) at a temperature of 37 ° C. On serum agar form delicate transparent colonies of medium size. In whey broth they grow in the form of turbidity and sediment at the bottom. Biochemically inactive, ferment only glucose and maltose, forming an acid, but not forming a gas. Extremely unstable in the environment, sensitive to temperature changes, die at temperatures below 37 °C. According to the capsular polysaccharide antigen, meningococci are divided into four main serogroups (groups A, B, C, D) and three additional (X, Y, Z). Meningococcal virulence factors: 1) adhesins - fimbriae (drank); 2) endotoxin; protects against intracellular digestion, ensuring the incompleteness of phagocytosis; due to the incompleteness of phagocytosis, intracellular reproduction of the pathogen occurs; 3) aggression enzymes - hyaluronidase, neuraminidase; 4) surface proteins with anti-lysozyme activity; 5) siderophores are cellular inclusions that actively bind ferric iron, competing with erythrocytes. Meningococci are pathogenic only for humans. Meningococcal infection is an anthroponotic infection, the source is a patient (or a bacteriocarrier). The main route of transmission is airborne. Clinical forms can be different: meningococcal nasopharyngitis, cerebrospinal meningitis, meningococcemia (meningococcal sepsis), meningococcal endocarditis, etc. After the disease, a stable species-specific antimicrobial immunity is formed. Young children have passive immunity due to IgG obtained from the mother. Diagnostics: 1) bacteriological examination; the material for the study is determined by the clinical form of the disease; medium - serum agar; 2) immunoindication: immunofluorescence, ELISA, precipitation reactions, latex agglutination; 3) serodiagnosis: RPHA with paired sera (for the diagnosis of generalized forms of infection). Treatment: etiotropic therapy: sulfonamides, penicillins, chloramphenicol. Specific prevention: 1) chemical meningococcal vaccine containing polysaccharide antigens of serogroups A and C (active antimicrobial immunity); 2) human immunoglobulin (passive antimicrobial immunity). 4. Gonococci They belong to the genus Neisseria, species N. gonorrhoeae. These are bean-shaped diplococci, in smears they are located intracellularly in the protoplasm of leukocytes, they look like coffee beans. They do not form spores, are immobile, form a microcapsule, Gram-negative. They are obligate aerobes. Gonococci are extremely demanding on nutrient media; they grow only on media containing human proteins (serum agar, ascites agar, etc.). On serum agar form small shiny colonies in the form of droplets. Biochemically inactive, break down only glucose (to acid). Gonococcal antigens: 1) protein antigens of the outer membrane; 2) lipopolysaccharide antigens of the cell wall. There is no generally accepted division into serogroups and serovars. Virulence factors: 1) adhesins - fimbriae (drank); 2) endotoxin; inhibits phagocytosis, providing intracellular location of gonococci; 3) aggression enzymes - hyaluronidase, neuraminidase. Pathogenic only for humans. They cause only specific nosological forms of purulent-inflammatory diseases. Gonococcal infection is an anthroponotic infection, the source of infection is a sick person, there is no carriage. The path of sexual transmission, it is possible to infect a newborn when passing through the birth canal of a sick mother. Clinical forms of gonococcal infection: 1) gonorrhea (urogenital, extragenital); 2) gonococcal septicopyemia; 3) specific conjunctivitis of newborns (occurs only when passing through the birth canal of a mother with gonorrhea). According to the duration of the course of gonorrhea and the severity of clinical signs, there are: 1) fresh gonorrhea (lasting no more than 2 months): a) sharp; b) subacute; c) torpid; 2) chronic gonorrhea (sluggish disease lasting more than 2 months or with an unspecified period). According to the clinical course, there are: 1) uncomplicated gonorrhea (purulent inflammation of the lower parts of the urogenital tract); 2) complicated gonorrhea (the process extends to the upper parts of the genitourinary system). The transferred disease does not leave stable immunity. Diagnostics: 1) in acute form: a) bacterioscopy of a smear of the discharge of the urethra, cervix; b) bacteriological examination; 2) in chronic form: a) bacterioscopy; b) bacteriological examination; c) serodiagnosis - RSK; d) immunoindication. A feature of serodiagnosis: the diagnosis is made qualitatively (by detection of antibodies in the serum of the subject) based on the results of a single reaction (without paired sera). This is due to the fact that post-infectious immunity is not formed in gonorrhea (there are no post-infectious antibodies). Treatment: etiotropic antibiotic therapy. Specific prophylaxis has not been developed. LECTURE No. 19. Gram-negative bacteria - causative agents of purulent-inflammatory diseases 1. Haemophilus influenzae Family Pasterellaceae, genus Haemophilus, species H. influenza. These are small or medium-sized straight rods, non-spore-forming, immobile, gram-negative, aerobes. In the body form a capsule. For cultivation, nutrient media containing blood (blood agar) or its preparations (chocolate agar) are required. In the environment, microorganisms quickly die from the action of temperatures above 55 ° C, sunlight, drying, and disinfectant solutions. Biochemical activity is weakly expressed. They break down mainly carbohydrates to acid (without the formation of gas). According to the ability to form indole, produce urease and ornithine decarboxylase, hemophilic influenzas are divided into six biovars. Antigenic structure: 1) somatic protein O-antigen; 2) capsular polysaccharide K-antigen; According to the structure of the capsular K-antigen, the species is divided into five serovars (denoted a, b, c, d, e). Serovar b is the most common causative agent of meningitis. Pathogenic factors: 1) endotoxin; 2) capsular polysaccharide with antiphagocytic activity. Does not produce exotoxin. Haemophilus influenzae can be part of the normal microflora of the mucous membrane of the oropharynx and upper respiratory tract, so the infection can occur as endogenous. With exogenous infection, it causes infections of the ENT organs and respiratory organs (otitis media, pneumonia), meningitis. The route of transmission is airborne. The source of infection is a patient or a bacteriocarrier (anthroponotic infection). Most often, the disease develops as a secondary infection with a decrease in the overall resistance of the organism due to the underlying disease. Bacterial meningitis caused by Haemophilus influenzae occurs most often in children aged 6 months to 3 years. This is due to the fact that in children under the age of 3 months, serum antibodies are detected, transmitted to them from the mother, but subsequently disappearing, and only by the age of 3-5 years bactericidal complement-dependent antibodies to the capsular polysaccharide of the pathogen reappear. Diagnostics: 1) bacteriological examination - the main method; material - sputum, cerebrospinal fluid, blood; medium - blood agar. It is necessary to differentiate from similar microorganisms of the same genus - representatives of the normal microflora of the nasopharynx and oral cavity; 2) express method - immunoindication using immunofluorescence reaction with specific type b serum (used in the diagnosis of meningitis). Etiotropic therapy is carried out with antibiotics, taking into account the sensitivity of the pathogen. Specific prophylaxis: chemical vaccine. 2. Pseudomonas aeruginosa Belongs to the family Pseudomonadaceae, genus Pseudomonas, species P. aerugenosa. The genus Pseudomonas, in addition to Pseudomonas, includes more than 20 species, many of which can also cause disease in humans. These are straight or slightly curved rods of medium size, motile (lophotrichous or monotrichous), gram-negative, obligate aerobes. They do not form spores, they have a thin mucous capsule. Pseudomonas aeruginosa is undemanding to nutrient media, grows well on artificial nutrient media. On meat-peptone broth, it grows in the form of turbidity with a grayish film on the surface. On dense nutrient media, large translucent colonies of a fluorescent greenish color are formed. At the same time, bluish-green water-soluble pigments - pyocyanin or fluorescein - diffuse into the medium. The ability of pseudomonads to form pigments is the most characteristic differential diagnostic feature. The culture of Pseudomonas aeruginosa when cultivated on nutrient media has a sour-sweet fragrant odor (specific odor of jasmine). Stable in the external environment. It is naturally resistant to antibiotics. Biochemical properties: 1) low saccharolytic activity, breaks down glucose to acid; 2) high proteolytic activity, decomposes some amino acids; 3) reduces nitrite to gaseous nitrogen; 4) liquefies gelatin. Metabolism is oxidative only. Antigenic structure: 1) somatic O-antigen, group-specific, according to its structure it is divided into serogroups; 2) flagellar H-antigen; 3) M-antigen of extracellular mucus. Pathogenic factors: 1) in the body can form a capsule-like substance with protective properties; 2) releases heat-labile exotoxin A, which has cytotoxic and dermonecrotic effects; 3) releases endotoxin; 4) some strains produce hemolysins and leukocidin; 5) has aggression enzymes such as plasmacoagulase, proteases, antielastase. Pseudomonas aeruginosa can live in the human intestine, found on the skin and mucous membranes. Most often, Pseudomonas aeruginosa infection is nosocomial. Source - the patient (or bacteriocarrier). Can cause various diseases. Especially often allocated with purulent-inflammatory complications of burn wounds. Immunity after infection is due to humoral and cellular mechanisms. Diagnosis: bacteriological examination; the material is determined by the clinical manifestations of the disease. Etiotropic therapy: 1) antibiotics (cephalosporins, aminoglycosides); 2) Pseudomonas aeruginosa bacteriophage; 3) Pseudomonas aeruginosa immune plasma; 4) killed therapeutic staphylo-Protein-Pseudomonas aeruginosa vaccine. 3. Klebsiella The genus Klebsiella includes several species pathogenic to humans. The most significant are K. pneumoniae, K. ozaenae, K. rhinoscleromatis. These are gram-negative rods of medium size that do not form spores. facultative anaerobes. In preparations, they are arranged singly, in pairs or in short chains. They do not have flagella, are immobile. Dispute does not form. These are true capsular bacteria: they form a capsule in the body and on nutrient media. The capsule has a polysaccharide structure. Undemanding to nutrient media. On dense nutrient media, they form characteristic dome-shaped turbid mucous colonies. When growing on meat-peptone broth, they cause uniform turbidity, sometimes with a mucous film on the surface. Klebsiella are resistant to environmental factors, thanks to the capsule they are stored for a long time in water, on objects, in rooms. They have a pronounced saccharolytic activity, ferment carbohydrates with the formation of acid and gas. According to biochemical properties, the genus is divided into six species. The following tests are used for differentiation: 1) glucose fermentation; 2) lactose fermentation; 3) the formation of urease; 4) utilization of citrate. Antigenic structure: 1) somatic O-antigen - group-specific; 2) capsular K-antigen. K antigens are shared with Escherichia and Salmonella antigens. Pathogenic factors: 1) have pronounced adhesive properties; 2) the main factor is a capsule that protects microorganisms from phagocytosis; 3) have a K-antigen that suppresses phagocytosis; 4) secrete endotoxin. Klebsiella is often found on the skin and mucous membranes, and therefore the development of an endogenous infection is possible. But exogenous infection is more common. Sources of infection can be a patient, a bacteriocarrier, objects of the external environment. Ways of transmission - airborne, contact-household. K. pneumoniae can cause pneumonia in humans, damage to the joints, meninges, urinary organs, purulent postoperative complications, and sepsis. K. ozaenae infects the mucous membrane of the upper respiratory tract and paranasal sinuses, causing them to atrophy. K. rhinoscleromatis affects the nasal mucosa, trachea, bronchi, pharynx, and larynx. Post-infection immunity is unstable. Diagnostics: 1) bacteriological examination; material - detachable affected mucous membranes; 2) immunoindication. Etiotropic therapy: 1) antibiotics, fluoroquinolones, taking into account the sensitivity of the pathogen; 2) killed therapeutic vaccine Solko-Urovak (for the treatment of urogenital infections); 3) VP-4 vaccine (for the treatment of respiratory tract infections). Specific prophylaxis: IRS19 vaccine. 4. Proteus Genus Proteus. The causative agent of purulent-inflammatory diseases is the species P. mirabilis. These are polymorphic gram-negative rods with rounded ends, facultative anaerobes. There is no capsule formation. They have peritrichous flagella. The H-forms of these bacteria are highly motile, although there are also immobile (O-forms). Undemanding to nutrient media. On meat-peptone agar, the H-form of the protea gives a characteristic creeping growth in the form of a delicate bluish-smoky veil (swarming phenomenon), covering the entire surface with a continuous coating without the formation of individual colonies. In a liquid nutrient medium, it grows in the form of diffuse turbidity. During cultivation, a putrefactive odor is characteristic. O-forms form large colonies with smooth edges. Some strains cause hemolysis of erythrocytes in blood media. They are stable in the environment, can remain viable in weak solutions of disinfectants. Widely distributed in nature. They are inhabitants of the intestines of humans and animals. Biochemical properties: 1) ferment glucose to acid; 2) do not decompose mannitol and lactose; 3) produce hydrogen sulfide; 4) liquefy gelatin, break down urea with the formation of ammonia; 5) have proteolytic and peptolytic activity. Antigenic structure: 1) somatic O-antigen - group-specific; 2) flagellar H-antigen - a specific variant. According to the H-antigen, proteins are divided into 110 serovars. Within the species, fagovars, bactericinovars, bacteriocinogenovars are distinguished. Pathogenic factors: 1) adhesins - drank; 2) endotoxin; 3) pathogenic amines - indole, skatole; 4) enzymes of aggression - proteases. Proteins in small quantities can be found in the intestines of a healthy person, so a protein infection can develop as an endogenous one. Their main habitat is objects of the external environment, rotting products, sewage, soil. Sources of infection for a person can be a patient and a bacteriocarrier. Bacteria are involved in the development of purulent-inflammatory diseases of the urinary tract, quickly spread over the burn surface, giving a characteristic putrid odor. Post-infection immunity is unstable. Diagnosis: the main method is bacteriological examination; the material is determined by the localization of the lesion. Sowing according to the Shushkevich method in a drop of condensed moisture of freshly cut meat-peptone agar; characteristic growth in the form of a veil over the entire surface of the medium. Etiotropic therapy: 1) antibiotics, nitrofurans, fluoroquinolones; 2) Proteus or coliproteus bacteriophage; 3) killed therapeutic staphylo-Protein-Pseudomonas aeruginosa vaccine. Specific prophylaxis has not been developed. LECTURE No. 20. Diphtheria 1. Morphology and cultural properties The causative agent belongs to the genus Carinobacterium, the species C. difteria. These are thin rods, straight or slightly curved, gram-positive. They are characterized by pronounced polymorphism. Club-shaped thickenings at the ends are metachromatic grains of volutin. These inclusions are located one at each end and can be detected by Neisser staining. In smears, bacteria are arranged at an angle in the form of V or X, which is due to their own "clicking" division. Spores and capsules do not form. Motionless. They have fimbriae. They are facultative anaerobes or aerobes. Being released into the external environment with saliva, films, diphtheria bacilli are able to remain viable on objects for several days. They tolerate drying well. Sensitive to antibiotics and disinfectants. Carinobacteria are demanding on nutrient media; serum media or media with the addition of blood are used for their cultivation. Roux medium (clotted serum) is used. On it, visible growth is observed after 10-12 hours, the colonies are convex, the size of a pinhead, grayish-white in color, with a smooth surface, do not merge with each other. For isolation, elective nutrient media are used with the addition of potassium tolurite in such a concentration that it does not inhibit the growth of corynobacteria, but inhibits the growth of the accompanying microflora. Colonies from gray to black are formed on blood-tolurite agar. On liquid media, growth is observed in the form of a film or turbidity with a precipitate. According to biochemical properties, the nature of growth on nutrient media, carinobacteria are divided into three biovars: 1) gravity; 2) mitis; 3) intermediate. For the differentiation of biovars, the following biochemical properties are taken into account: 1) the breakdown of carbohydrates; 2) recovery of nitrates; 3) cleavage of cysteine. Antigenic structure: 1) group polysaccharide antigen; 2) specific O-antigen; 3) variant-specific K-antigen. According to the K-antigen, the species is divided into 11 serovars. Virulence factors: 1) villi, fimbria or pili (responsible for the ability to adhere); 2) colonization and invasion (due to enzymes such as neuraminidase, hyaluronidase, proteases); 3) cord factor (impairs phosphorylation of the processes of respiration of macroorganism cells); 4) the leading factor is exotoxin. This is a protein consisting of peptides A and B. Peptide B acts as an acceptor, it recognizes the corresponding cell receptors, binds to them and forms an intramembrane channel through which peptide A penetrates into the cell. Peptide A implements the biological activity of the toxin. 2. Pathogenesis Ways of transmission - airborne, contact-household. The disease develops in individuals who do not have antitoxic immunity. The causative agent penetrates through the mucous membranes of the oropharynx, less often - the eyes, genitals, skin, wound surface. At the site of the entrance gate, the pathogen attaches to the corresponding receptors of epithelial cells, causing an inflammatory process. Then colonization and release of exotoxin (histotoxin) occur. The toxin blocks protein synthesis enzymes in host cells, which leads to their death. This leads to necrosis and death. The pathogen itself remains at the site of the entrance gate of infection, and the pathogenesis and clinical picture are determined by the action of exotoxin, which has a general and local effect. The pathomorphological manifestation of the interaction of macro- and microorganism in diphtheria is fibrinous inflammation. Exotoxin first directly affects epithelial cells, and then nearby blood vessels, increasing their permeability. In the exudate leaving the vessels, fibrinogen is detected, during the coagulation of which, grayish-white membranous plaques are formed on the surface of the mucous membrane, tightly soldered to the surrounding tissue. They are difficult to remove; when they are torn off, an erosive surface is exposed. The growth of these films and their transition to the airways lead to the development of true croup and asphyxia. Then the following are involved in the inflammatory process: 1) regional lymph nodes (lymphadenitis); 2) vessels (the toxin quickly penetrates into the blood, and paretic vasodilation occurs, which leads to stagnation and stasis); 3) heart (the toxin affects the myocardium, the conduction system of the heart, which leads to paralysis of the heart muscle); 4) adrenal cortex selective lesion, which has a secondary adverse effect on the cardiovascular system; 5) kidneys (nephritis); 6) peripheral nervous system - polyneuritis, paresis, paralysis (first of all - paresis of the soft palate); 7) immune system (antibodies are absent on the 5-7th day). The strength of a toxin is measured in DLM. 1 DLM is the minimum amount of toxin that, when administered subcutaneously to a guinea pig weighing 250 g, causes its death on the 4th-5th day with a characteristic pathological and anatomical picture: the adrenal glands are enlarged, sharply hyperemic, with hemorrhagic exudate in the cavities. After the illness, unstable and short-lived antibacterial immunity and persistent antitoxic immunity are formed. The most susceptible to diphtheria are children from 1 to 4 years of age. 3. Diagnostics. Prevention. Treatment Microbiological diagnostics 1. The main method is bacteriological examination. 2. Determination of the toxigenicity of the species culture (Vagai precipitation reaction). Methods for determining toxigenicity: 1) biological sample - guinea pigs are injected intradermally with a broth culture; 2) setting ELISA; 3) the use of DNA probes, which determine the presence of a toxic operon in the genome of the isolated culture; 4) Wagai precipitation reaction. Subject to research: 1) persons with suspected diphtheria; 2) patients with various diseases of the ENT organs. Features of bacteriological research in diphtheria: 1) the material is sown on elective nutrient media; 2) the mucous membranes of the nose, pharynx, genitals, skin as part of the normal microflora contain various representatives of the genus Carinobacterium. They are conditionally pathogenic, united by the concept of diphtheroids. In debilitated patients, with secondary immunodeficiency, in cancer patients, various purulent-inflammatory processes can be caused. In the course of a bacteriological study, it is necessary to differentiate diphtheria carinobacteria from diphtheroids. Differences between diphtheroids and diphtheria pathogens: 1) differences in morphological properties. Diphtheroids in smears are arranged randomly or in the form of a palisade. There are no volutin grains in the cytoplasm; 2) differences in biochemical activity; 3) to identify differences in antigenic properties, an agglutination reaction is used for identification with a species differentiated serum; 4) sensitivity to bacteriophage. Cultural properties do not differ. Etiotropic therapy: antitoxic antidiphtheria serum; administered at a dose of 10-000 AU (depending on the age and severity of the disease). 1 AU is the minimum amount of serum that will neutralize 100 DLF diphtheria toxin. Serotherapy is effective in the early period of the disease, until the toxin is fixed in the cells of the body and the tissues are not significantly damaged. Prevention: 1) active. Vaccines are used: AD (diphtheria toxoid), ADS, ADSM, DTP. DTP vaccination is carried out three times for children at the age of 3 months. Revaccination is carried out under the control of determining the content (titer) of serum antitoxins using the reaction of RPHA with diphtheria anatotoxic erythrocyte diagnosticum. If TPHA is positive at a dilution of 1:20 or more, the titer is considered protective; 2) passive. It is carried out in the foci of the disease with antitoxic serum, the dose of which is determined by the form and severity of the disease. LECTURE No. 21. Tuberculosis 1. Morphology and cultural properties The causative agent belongs to the genus Mycobacterium, species M. tuberculesis. These are thin sticks, slightly curved, do not form spores or capsules. The cell wall is surrounded by a layer of glycopeptides called mycosides (microcapsules). Tuberculosis bacillus is difficult to perceive conventional dyes (according to Gram stained for 24-30 hours). Gram-positive. Tuberculosis bacillus has features of the structure and chemical composition of the cell wall, which are reflected in all biological properties. The main feature is that the cell wall contains a large amount of lipids (up to 60%). Most of them are mycolic acids, which are included in the framework of the cell wall, where they are in the form of free glycopeptides that are part of the cord factors. Cord factors determine the nature of growth in the form of bundles. The cell wall contains lipoarabinomanan. Its terminal fragments - cap - determine the ability of the pathogen to specifically bind to macrophage receptors. Mycobacterium tuberculosis stained by Ziehl-Neelsen. This method is based on the acid resistance of mycobacteria, which is determined by the characteristics of the chemical composition of the cell wall. As a result of treatment with anti-tuberculosis drugs, the pathogen may lose acid resistance. Mycobacterium tuberculosis is characterized by pronounced polymorphism. In their cytoplasmic membrane, characteristic inclusions are found - Fly grains. Mycobacteria in the human body can transform into L-forms. By type of energy production aerobes. According to the temperature requirements - mesophiles. Their reproduction is very slow, the generation time is 14-16 hours. This is due to the pronounced hydrophobicity, which is due to the high content of lipids. This makes it difficult to supply nutrients to the cell, which reduces the metabolic activity of the cell. Visible growth on Wednesdays - 21-28 days. Mycobacteria are demanding on nutrient media. Growth factors - glycerin, amino acids. They grow on potato-glycerin, egg-glycerin and synthetic media. All these media must be supplemented with substances that inhibit the growth of contaminating flora. On dense nutrient media, characteristic colonies are formed: wrinkled, dry, with jagged edges, do not merge with each other. In liquid media, they grow in the form of a film. The film is initially tender, dry, thickens with time, becomes bumpy-wrinkled with a yellowish tint. The medium is not transparent. Tuberculosis bacteria have a certain biochemical activity, and the study of it is used to differentiate the causative agent of tuberculosis from other members of the group. Pathogenic factors: 1) mycolic acids; 2) cord factor; 3) sulfatides; 4) mycosides; 5) lipoarabinomanan. 2. Pathogenesis The causative agent of tuberculosis enters the body as part of fine aerosols. The pathogen must enter the alveoli, where they are absorbed by resident macrophages, the relationship with which determines the further development of the infection. Tuberculosis is a classic intramacrophage infection. Inside macrophages, tuberculosis bacteria are resistant to bactericidal factors of phagocytes due to a powerful lipid membrane. As a result of the interaction of mycobacteria and macrophages, inflammation of the granulomatous type develops under the influence of virulence factors. A granuloma develops immediately after infection, but later it receives a powerful impetus to development when T-lymphocytes sensitized to the pathogen appear in the body. Pre-immune granuloma after 2-3 weeks under the influence of T-lymphocytes turns into a specific (post-immune), which is called tuberculoma. From the lungs, the tubercle bacillus enters the regional lymph nodes, then into the bloodstream. Further events are associated with specific inflammation, which is based on an allergic reaction to bacterial antigens. The route of infection is airborne. The source is a sick person who, in the acute period, excretes tubercle bacilli with sputum. Pulmonary tuberculosis is the most common, but the intestines, the musculoskeletal system, and the genitourinary system, etc., can also be affected. There are two pathogenetic variants of tuberculosis. 1. Primary tuberculosis. Occurs in individuals who have not previously had contact with the pathogen. Infection occurs during childhood or adolescence. It develops without allergy to the pathogen. In the introduction zone, the pathogen is captured by macrophages, a nonspecific granulomatous reaction develops. Bacteria easily pass this barrier, quickly penetrate into the regional lymph nodes, blood and various organs. After 2-3 weeks, a primary tuberculosis complex is formed, which includes: 1) primary affect - a focus in the lung tissue; 2) lymphadenitis - inflammation of regional lymph nodes; 3) lymphangitis - inflammation of the lymphatic vessels. Most often, it heals itself, undergoes fibrosis and calcification (Gon's focus). Bacteria persist in this focus, but are not released into the external environment. In other cases, acute tuberculosis develops. 2. Secondary tuberculosis. Runs chronically. It occurs when the primary focus is reactivated (after 5 years or more). Reinfection from the outside is also possible. The development of secondary tuberculosis is facilitated by unfavorable living conditions, chronic diseases, alcoholism, stress, etc. Features of immunity in tuberculosis: 1) non-sterile, supported by those bacteria that persist in the body; 2) unstable, i.e., does not protect against reactivation of endogenous infection and reinfection from the outside; 3) antibodies are formed, but they have no protective value; 4) the main mechanism of immunity is cellular; infectious allergy is of primary importance. 3. Diagnostics. Prevention. Treatment Diagnostics: 1) microscopic examination. Two smears are made from sputum. One is stained by Ziehl-Neelsen, the second is treated with fluorochrome and examined using direct fluorescence microscopy. Is a reliable method; 2) bacteriological research. Is required. The disadvantage is that mycobacteria grow slowly on nutrient media (4 weeks). During the study, sensitivity to tuberculostatic drugs is determined. Apply accelerated methods for the detection of mycobacteria in crops, for example, according to the Price method. Microcolonies make it possible to see the presence of the cord factor, when the bacteria that formed it are folded into braids, chains, bundles; 3) polymer chain reaction (PCR). It is used for extrapulmonary forms; 4) serodiagnosis - ELISA, RPHA, fluorescence reaction. Not a leading method; 5) Mantoux test with tuberculin - an allergological method. Tuberculin is a preparation from a killed culture of mycobacteria. The sample is placed during the selection of persons for revaccination to assess the course of the tuberculosis process; 6) microculturing on slides in Shkolnikov's medium; 7) biological method. It is rarely used when the pathogen is difficult to isolate from the test material. Material from the patient infects laboratory animals (guinea pigs, rabbits). Observation is carried out until the death of the animal, and then the punctate of its lymph nodes is examined. Specific prophylaxis: live BCG vaccine. Vaccination is carried out in the maternity hospital on the 4th-7th days of life by the intradermal method. Revaccination is carried out for persons with a negative tuberculin test with an interval of 5-7 years until the age of 30. In this way, infectious immunity is created, in which a delayed-type hypersensitivity reaction occurs. Treatment Most antibiotics have no effect on Mycobacterium tuberculosis, so tuberculostatic drugs are used. There are two types of drugs used: 1) first-line drugs: isoniazid, pyrazinamide, streptomycin, rifampicin, ethambutol, ftivazid; 2) second-line drugs (with the ineffectiveness of first-line drugs): amikacin, kanomycin, sodium aminosalicylate (PAS), dapsone, cycloserine, etc. Features of therapy for tuberculosis: 1) treatment should be started as early as possible, immediately after the detection of the disease; 2) therapy is always combined - at least two drugs are used; 3) it is carried out for a long time (4-6 months), which is associated with a long life cycle of mycobacteria; 4) must be continuous, since interruptions lead to the formation of resistance of the pathogen and the chronization of the process. LECTURE No. 22. Rickettsia group 1. Characteristics of the group Rickettsia are a separate class, which is divided into subclasses a1, a2, b and g. a1 includes the family Rickettsiaceae, of which two genera are the most important. 1. Genus Rickettsia, species are divided into two groups: 1) a group of typhus: a) R. provacheka - the causative agent of epidemic (lousy) typhus; b) R. typhi - the causative agent of endemic (rat-flea) typhus; 2) a group of tick-borne rickettsiosis: a) R. rickettsi - the causative agent of rocky mountain fever; b) R. conori - the causative agent of hemorrhagic fever; c) R. sibirika is the causative agent of North Asian rickettsiosis. 2. The genus Erlihia, isolated species: E. canis and E. sennetsu (may be the causative agents of infectious mononucleosis). a2 includes the family Bartonellaceae, genus Bartonella, subdivided into species: 1) B. kvintana - the causative agent of five-day (trench) fever; 2) B. hensele - the causative agent of "cat-scratch disease". g includes the genus Coxiella, the species C. burneti, the causative agent of Q fever. Rickettsiae are bacteria whose hallmark is obligate intracellular parasitism. They are similar in structure to Gram-negative bacteria. They have their own enzyme systems. Motionless, no spores or capsules. Rickettsia are characterized by pronounced polymorphism. There are four forms: 1) form A - coccal, oval, located singly or in the form of dumbbells; 2) form B - sticks of medium size; 3) form C - bacillary rickettsia, large sticks; 4) form D - filiform, can give branches. Morphology depends on the stage of the infectious process. In the acute form, forms A and B are mainly found, in the chronic, sluggish form - C and D. The interaction of rickettsia with the cell includes several stages. 1. Adsorption on the receptors of the corresponding cells. 2. After attachment, the membrane invaginates, the rickettsia sinks into the cell as part of a vacuole, the walls of which are formed by the cell membrane. 3. Then there are two options: 1) some types of rickettsia continue to remain inside the vacuole and multiply there; 2) others lyse the membrane and lie freely in the cytoplasm. 4. Rickettsia multiply intensively, the membrane is destroyed, and they leave the cell. Obligate intracellular parasitism of rickettsia is realized at the cellular level. Since rickettsiae are intracellular parasites, they do not multiply in nutrient media. For their cultivation, the same methods are used as for the cultivation of viruses: 1) tissue infection; 2) infection of chicken embryos; 3) in the body of experimental animals; 4) in the body of ectoparasites. 2. Rickettsioses The most common rickettsiosis is epidemic typhus. The causative agent is R. Provacheka. The source of infection is a sick person. The carrier is body and head lice. These are polymorphic microorganisms. Reproducing in host cells, they form a microcapsule. Aerobes. Cultivated in chicken embryos. They have two antigens: 1) group-specific (has immunogenic properties and is protective); 2) corpuscular, species-specific (available only in this species). The disease begins after the pathogen enters the bloodstream. Rickettsiae adhere to capillary endotheliocytes. In the cytoplasm of these cells, they multiply. After the cells are destroyed, a new generation of rickettsiae enters the bloodstream. Damage to the capillaries leads to the formation of blood clots and granulomas. The most dangerous localization of the lesion is the central nervous system. A rash appears on the skin. In addition to direct action, rickettsia secrete endotoxin, which causes capillary paresis. After the disease, intense antimicrobial immunity remains. Diagnostics: 1) serodiagnosis - the main method (RPHA, RSK with a diagnosticum from R. Provacheka); 2) bacteriological examination; test material - blood; carried out only in special regime laboratories; 3) PCR diagnostics. Specific prophylaxis: live typhoid vaccine. Etiotropic therapy: antibiotics - tetracyclines, fluoroquinolones. The most common rickettsioses include endemic (rat-flea) typhus. Pathogen - R. typhi. The source of infection is rat fleas, lice, gamasid mites. Ways of infection - transmissible, airborne. The pathogenesis and clinical manifestations of the disease are similar to epidemic typhus. R. typhi have a species-specific antigen by which they are differentiated from other rickettsiae. Diagnostics: 1) biological sample - infection with material from sick guinea pigs; 2) serodiagnosis - RSK, IF. It is necessary to say about Q-fever. The causative agent is C. burneti. The source of infection is livestock. Ways of transmission - alimentary, contact-household. These are small rod-shaped or coccoid formations, stained according to Romanovsky-Giemsa in a bright pink color. They form L-shapes. Cultivated in the yolk sac of the chick embryo. They have two antigens: soluble and corpuscular. Resistant to environmental factors. Rickettsemia occurs after C. burneti enters the body. The reproduction of microorganisms occurs in histiocytes and macrophages, after the destruction of which generalization of the process and toxinemia are noted. In the process of infection, a delayed-type hypersensitivity reaction develops, and a tense immunity is formed. The disease is characterized by an unclear clinical picture. Diagnostics: 1) serological examination (RSK, RPGA); 2) skin-allergic test (as a retrospective diagnostic method). Specific prophylaxis: live vaccine M-44. Treatment: antibiotics - tetracyclines, macrolides. LECTURE No. 23. ARVI pathogens 1. Influenza viruses They belong to the family of orthomyxoviruses. Influenza viruses of types A, B and C are isolated. The influenza virus has a spherical shape, with a diameter of 80-120 nm. The nucleocapsid of helical symmetry is a ribonucleoprotein strand (NP protein) folded in the form of a double helix that makes up the core of the virion. RNA polymerase and endonucleases are associated with it. The core is surrounded by a membrane consisting of protein M, which connects the ribonucleoprotein strand to the lipid double layer of the outer shell. Among the proteins of the supercapsid envelope, two are of great importance: 1) neuraminidase - a receptor protein that ensures the penetration of the virus into the cell; 2) hemagglutinin. Performs a receptor function, has an affinity for glycoprotein receptors of cells of the mucous membrane of the respiratory tract. The virus genome is represented by a minus-strand fragmented RNA molecule. Replication of orthomyxoviruses is primarily realized in the cytoplasm of the infected cell. Synthesis of viral RNA is carried out in the nucleus. The host cells provide the virus with new RNA transcripts, the 5' ends of which are used to cap the 5' ends of the viral messenger RNA. Influenza A, B, and C viruses differ from each other in type-specific antigen associated with M and NP proteins. A narrower specificity of type A virus is determined by hemagglutinin (H-antigen). There is a high antigenic variability within the genus. The variability of the H-antigen determines: 1) antigenic drift - changes in the H-antigen caused by point mutations in the gene that controls its formation; 2) antigenic shift - a complete replacement of a gene, which is based on recombination between two genes. Initially, the pathogen replicates in the epithelium of the upper respiratory tract, causing the death of infected cells. Through damaged epithelial barriers, the virus enters the bloodstream. Viremia is accompanied by multiple lesions of the capillary endothelium with an increase in their permeability. In severe cases, extensive hemorrhages are observed in the lungs, myocardium and various parenchymal organs. The main symptoms include a rapid increase in body temperature with concomitant myalgia, runny nose, cough, headaches. The causative agent is ubiquitous, an increase in incidence is observed in the cold months. The main route of transmission of the pathogen is airborne. Children and the elderly are most susceptible. Laboratory diagnostics: 1) express diagnostics - determination of virus antigens in the cytoplasm of the epithelium of the nose and nasopharynx in smears-prints by ELISA; 2) infection of cell cultures or chicken embryos with nasal discharge, sputum or swabs from the nasopharynx (obtained in the first days of illness); 3) serodiagnostics (RCC, RTGA, enzyme activity inhibition reaction). Specific prevention: 1) for passive immunization - human anti-influenza immunoglobulin; 2) for active immunization - live and inactivated vaccines. Treatment: amantadine derivatives (remantadine). 2. Parainfluenza. PC viruses Parainfluenza virus and RS virus belong to the Paramyxoviridae family. These are spherical viruses with helical symmetry. The average size of the virion is 100-800 nm. They have a supercapsid membrane with spiny processes. The genome is represented by a linear non-segmented RNA molecule. The RNA is associated with a major (NP) protein. The shell contains three glycoproteins: 1) HN, which has hemagglutinating and neuraminidase activity; 2) F, responsible for fusion and exhibiting hemolytic and cytotoxic activity; 3) M-protein that forms the inner layer of the viral envelope. Virus replication is fully realized in the cytoplasm of host cells. The human parainfluenza virus belongs to the genus Paramyxovirus. Viruses are characterized by the presence of their own RNA-dependent RNA polymerase (transcriptase). Based on the differences in the antigenic structure of the HN, F and NP proteins of human parainfluenza viruses, four main serotypes are distinguished. Types 1, 2, and 3 are antigenically related and cross-react with mumps antigen. Type 4 viruses do not have a pronounced antigenic relationship. The pathogen reproduces in the epithelium of the upper respiratory tract, from where it enters the bloodstream, causing viremia. Clinical manifestations in adults most often occur in the form of catarrhs of the upper respiratory tract. In children, the clinical picture is more severe, often with symptoms of intoxication. The disease is most severe in young children. The main route of transmission of the parainfluenza virus is airborne. The source of infection is the patient (or virus carrier). Laboratory diagnostics: 1) express diagnostics - detection of antigens in the cells of the nasal passages using ELISA; 2) isolation of the pathogen in monolayer cultures of the kidneys of the embryo of humans or monkeys; 3) serodiagnosis (RSK, RN, RTGA with paired sera of sick people). Treatment: no specific drug therapy is available. Specific prophylaxis is not applied. PC virus is the main causative agent of lower respiratory tract infections in newborns and young children. Belongs to the genus Pneumovirus. It is characterized by low resistance, virions are prone to self-destruction, in a purified form they show pronounced polymorphism. There are three small types of PC virus, antigenic differences between which causes a specific surface antigen. The pathogen replicates in the epithelium of the airways, causing the death of infected cells, and exhibits pronounced immunosuppressive properties, which explains the high frequency of secondary bacterial infections. PC virus causes annual epidemic respiratory tract infections in newborns and young children; adults may be infected, but the course of infection is mild or asymptomatic. The main route of transmission is airborne. After recovery, unstable immunity is formed. Laboratory diagnostics: 1) express diagnostics - determination of virus antigens in the nasal discharge using ELISA; 2) specific antigens are detected in RSK and RN. Etiotropic therapy has not been developed. 3. Adenoviruses The family Adenoviridae includes two genera - Mastadenovirus (mammalian viruses) and Aviadenovirus (avian viruses); the first includes about 80 species (serovars), the second - 14. The family includes viruses with a naked capsid (there is no outer shell), a cubic type of symmetry. The size of the virion is 60-90 nm. The genome is represented by a linear double-stranded DNA molecule. The mature virus consists of 252 capsomeres, including: 1) hexons containing type-specific antigenic determinants, acting upon the release of hexons in the composition of the virion, responsible for the manifestation of the toxic effect; 2) pentons containing small antigens of the virus and a reactive soluble antigen of the family, which determine the hemagglutinating properties of viruses. Antigenic structure: 1) surface antigens of structural proteins (species- and type-specific); 2) hexon antigens (group-specific); 3) complement-fixing antigen (identical for different serotypes). The main routes of transmission are airborne and contact. The symptomatology of lesions is due to the reproduction of the pathogen in sensitive tissues. According to the type of lesions of sensitive cells, three types of infections are distinguished: 1) productive (lytic). Accompanied by cell death after the release of the daughter population; 2) persistent. It is observed when the rate of reproduction slows down, which makes it possible for tissues to compensate for the loss of infected cells due to the normal division of uninfected cells; 3) transforming. In tissue culture, cells are transformed into tumor cells. The main clinical manifestations of adenovirus infections. 1. Most often - SARS, occurring as flu-like lesions. The peak incidence occurs in the cold season. Outbreaks are possible throughout the year. 2. Pharyngoconjunctivitis (pharyngoconjunctival fever). The peak incidence occurs in the summer months; the main source of infection is the water of pools and natural reservoirs. 3. Epidemic keratoconjunctivitis. Lesions are caused by infection of the cornea during injuries or medical manipulations. Possible erosion of the cornea up to loss of vision. 4. Infections of the lower respiratory tract. Laboratory diagnostics: 1) isolation of the pathogen by inoculation into cultures of human epithelial cells; the investigated material - discharge of the nose, pharynx, conjunctiva, feces; 2) detection of virus antigens in cells by immunofluorescence microscopy; 3) RSK, RTGA and RN of the cytopathic effect in cell culture. Treatment: no specific drug therapy is available. Specific prophylaxis: live vaccines containing attenuated viruses of the dominant serotypes. 4. Rhinoviruses They belong to the Picornaviridae family. Virions have a spherical shape and a cubic type of symmetry. Size 20-30 nm. The genome is formed by a positive RNA molecule that is not segmented. The size of the molecule is small. An RNA molecule is linked to one protein molecule. The capsid membrane consists of 32 capsomeres and 3 large polypeptides. There is no supercapsid membrane. Virus replication takes place in the cytoplasm. The assembly of host cells and the filling of the capsid are also carried out in the cytoplasm; the release of the virus is followed by cell lysis. Viruses lose their infectious properties in an acidic environment. Well preserved at low temperatures. The temperature required for replication is 33 °C, its increase above 37 °C blocks the last stage of reproduction. Rhinoviruses are divided into two large groups according to their ability to reproduce in cells: 1) group H viruses. They multiply and cause cytopathic changes in a limited group of diploid cells, the human embryo and a special line (K) of HeLa cells; 2) group M viruses. They multiply and cause cytopathic changes in the cells of the kidneys of monkeys, the human embryo and various continuous cell lines of human cells. Under optimal cultivation conditions, a cytopathic effect is manifested. Antigenic structure: 1) according to the structure of a single type-specific antigen, 113 immunologically heterogeneous groups are distinguished; group-specific antigen is absent; 2) in humans, rhinovirus infection causes the production of neutralizing antigens and a state of immunity. The main route of transmission is airborne, the reservoir is a sick person (the pathogen is released within 1-2 days before the onset of symptoms and 2-3 days after the onset of the disease). Rhinoviruses are localized in the epithelial cells of the nasal mucosa with abundant secretions, and in children - in the bronchial mucosa, causing a runny nose, bronchitis, bronchopneumonia. After the disease, a short-term immunity remains, which is effective only against a homologous strain. It is determined by secretory immunoglobulins of the IgA type. Laboratory diagnostics: 1) isolation of viruses in cell cultures infected with nasal discharge; 2) express diagnostics - immunofluorescent method; allows to detect viral antigen in the cytoplasm of mucosal epithelial cells. Treatment: no specific antiviral therapy is available, treatment is symptomatic. Specific prophylaxis: Immunoprophylaxis is not carried out due to the large number of serological variants of the pathogen. 5. Reoviruses. PC viruses Reoviruses belong to the Reoviridae family. Virions are spherical, 60-80 nm in diameter. The capsid is built according to the icosahedral type of symmetry. Double-stranded RNA consists of ten fragments. There are eight separate proteins in the inner and outer capsids. One of the proteins of the outer capsid is responsible for binding to specific cell receptors, with the help of another, the virus enters the host cell. Virus replication occurs in the cytoplasm of host cells. Reoviruses are cultivated in various cell cultures. Cytopathic action appears late and resembles nonspecific degeneration of the cell monolayer. There are three serotypes of reoviruses. They have a common complement-fixing antigen and type-specific antigens (outer capsid protein). Viruses have hemagglutinating activity. The main route of transmission is airborne. Reoviruses primarily reproduce in the epithelial cells of the mucous membrane of the mouth, pharynx, small intestine, regional lymph nodes, from where they enter the lymph and blood. Viruses are able to pass through the placenta and have an embryopathic effect. Laboratory diagnostics: 1) isolation of the virus in cell culture and in newborn mice; 2) identification of the virus - in the neutralization reaction and RTGA; 3) serodiagnosis (RTGA). Specific prophylaxis and etiotropic therapy have not been developed. PC virus. Belongs to the family Paramyxoviridae, genus Pneumovirus. The family includes "dressed" viruses with helical symmetry, the genome of which is formed by a linear non-segmented RNA molecule associated with a major (NP) protein; the average size of the virion is 100-800 nm. The shell contains: 1) HN-glycoprotein. It has hemagglutinating and neuraminidase activity; 2) F-glycoprotein. Responsible for the merger. Shows hemolytic and cytotoxic activity; 3) M-protein. Forms the inner layer of the viral envelope. Virus replication is fully realized in the cytoplasm of host cells. In infected cell cultures, two antigens are isolated: 1) antigen A is resistant to treatment with ether, induces the synthesis of neutralizing and complement-fixing antigens; 2) antigen B induces the synthesis of complement-fixing antigens. RS virus is the main causative agent of lower respiratory tract infections in newborns and young children. The pathogen replicates in the epithelium of the airways, causing the death of infected cells. The PC virus is characterized by low resistance, virions are prone to self-destruction, in a purified form they show pronounced polymorphism, taking several forms. After recovery, unstable immunity is formed. The main route of transmission is airborne. Laboratory diagnostics: 1) isolation of the PC virus on human cell lines; 2) express diagnostics - determination of the antigen of the virus in the nasal discharge and mucosal cells using ELISA; 3) isolation of specific antigens in CSC and RN. Treatment: etiotropic therapy is absent. Treatment is symptomatic. There is no specific prevention. LECTURE No. 24. Causative agents of viral airborne infections 1. Measles and mumps viruses The mumps virus and the measles virus belong to the Paramixoviridae family. Virions have a spherical shape with a diameter of 150-200 nm. In the center of the virion is a nucleocapsid with a helical symmetry type, surrounded by an outer shell with spiny processes. Viral RNA is represented by a single-stranded negative strand. The nucleocapsid is covered by a matrix protein, which consists of two lipid layers and three viral specific proteins. The mumps virus belongs to the genus Paramyxovirus. Viral infection is characterized by a predominant lesion of the parotid salivary glands and the ability to cause epidemic outbreaks. Antigenic structure: 1) internal NP protein; 2) surface NH- and F-glycoproteins. Initially, the pathogen reproduces in the epithelium of the nasopharynx, then penetrates into the bloodstream and during the period of viremia penetrates into various organs: parotid glands, testicles, ovaries, pancreas, thyroid glands, head and other organs. Primary reproduction in the epithelium of the parotid glands is also possible. The main route of transmission is airborne. Laboratory diagnostics: isolation of the virus from the cerebrospinal fluid, saliva and punctate glands and cultivation on chicken embryos and chicken fibroblast cell cultures. Means of specific drug therapy are absent. Specific prevention: 1) live and killed vaccine; 2) specific immunoglobulin. The measles virus belongs to the genus Morbillivirus. Antigenic structure: 1) hemagglutinin (H); 2) peptide F; 3) nucleocapsid protein (NP). The main ways of transmission are airborne, less often contact. Initially, the virus multiplies in the epithelium of the upper respiratory tract and regional lymph nodes, and then penetrates into the bloodstream. Viremia is short-lived. The causative agent is hematogenously distributed throughout the body, fixing in the reticuloendothelial system. The activity of immune mechanisms aimed at the destruction of infected cells leads to the release of the virus and the development of a second wave of viremia. The tropism of the pathogen to epithelial cells leads to secondary infection of the conjunctiva, mucous membranes of the respiratory tract and oral cavity. Circulation in the bloodstream and emerging protective reactions cause damage to the walls of blood vessels, tissue edema and necrotic changes in them. Laboratory diagnostics: 1) detection of multinucleated cells and pathogen antigens (in the immunofluorescence reaction) in the discharge of the nasopharynx; 2) isolation of the virus on primary trypsinized cultures of monkey kidney cells or human embryos; 3) detection of an increase in antigen titers during convalescence. Treatment: no specific therapy is available. Specific prevention: 1) human measles immunoglobulin; 2) live attenuated vaccine. 2. Herpes virus The Herpesviridae family includes subfamilies: 1) a-herpesviruses (types I and II, herpes zoster); 2) b-herpesviruses; 3) g-aherpesviruses. They belong to DNA viruses. DNA is double-stranded, linear. The genome consists of two fragments: long and short. The DNA strand is wound around a central protein culture. The capsid shell is built from simple proteins and has a cubic symmetry type. There is a supercapsid membrane (lipid membrane with a layer of glycoproteins), heterogeneous in structure, forms spiny processes. Herpes viruses are relatively unstable at room temperature, heat-labile, and rapidly inactivated by solvents and detergents. a-herpes type I causes aphthous stomatitis in early childhood, labial herpes, less often - herpetic keratitis and encephalitis. a-herpes type II causes genital herpes, neonatal herpes, is a predisposing factor for the development of cervical cancer. Herpes zoster is the causative agent of shingles and chicken pox. This is a typical herpes virus infection. It is clinically manifested by the appearance of vesicles on the skin along the branches of the corresponding nerves. The disease is severe, but recovery is quick. After an infection, lifelong immunity remains. However, relapses of the disease associated with the persistence of the virus in the nerve ganglia are possible. After suffering a herpes virus disease, the virus persists for life in the nerve ganglia (often the trigeminal nerve). With a decrease in the body's defenses, a viral infection develops. b-herpes (cytomegalovirus) during reproduction in culture cells causes cytopathic changes. It has an affinity for the cells of the salivary glands and kidneys, causing the formation of large multinuclear inclusions in them. With the development of the disease, viremia, damage to internal organs, bone marrow, central nervous system, and the development of immunopathological diseases take place. g-herpes virus (Epstein-Bar virus) causes infectious mononucleosis. It may be a predisposing factor in the development of tumors. Diagnostics: 1. a-herpes virus: 1) identification of characteristic multinucleated giant cells with inclusion bodies in scrapings from the affected area; 2) cultivation in chicken embryos; 3) biological sample; 4) serological studies (RSK, ELISA); 5) method of direct immunofluorescence with monoclonal antigens. 2. b-herpes virus: 1) detection of large cytomegalovirus cells in urine and saliva; 2) cultivation in the culture of human embryonic fibroblasts; 3) serological examination (RSK); 4) immunofluorescence. 3. g-herpes virus: 1) virus isolation in fibroblast culture; 2) microscopy of smears of urine sediment, saliva to identify typical giant cells; 3) serological methods (RSK, RPGA and RN). Treatment: 1) antiviral drugs (acyclovir); 2) interferon. 3. Rubella virus Belongs to the family Togaviridae, genus Rubivirus. They are spherical enveloped viruses with an icosahedral nucleocapsid enclosed in a lipid envelope. The average size of rubiviruses is 60 nm. The surface of viruses is covered with glycoprotein spicules containing hemagglutinins. The genome is formed by a single-stranded +RNA molecule. RNA retains infectivity after isolation from the virion. The replicative cycle is realized in the cytoplasm of cells, where eosinophilic inclusions are detected. After adsorption and deproteinization, the viral RNA functions as a messenger RNA (mRNA) for the synthesis of viral proteins, which are formed by proteolytic "cutting" of the polyprotein. The rubella virus has two antigens: 1) nucleoprotein associated with the capsid; 2) supercapsid shell protein. The virus is represented by one serotype with hemagglutinating, hemolytic and weakly expressed neuraminidase activity. In humans, the virus causes rubella, an acute infectious disease commonly seen in children. Rubella is a highly contagious, widespread infection; the source is a sick person; the main route of transmission of the pathogen is airborne. Upon recovery, lifelong immunity is formed. The pathogenesis of a typical form includes the development of acute inflammatory reactions in the upper respiratory tract and the circulation of the pathogen in the bloodstream with subsequent damage to various organs, including the placenta during pregnancy. A characteristic sign of the disease is a maculopapular rash of a pale pink color, most abundant on the extensor surfaces of the limbs, back and buttocks. After 2-3 days, the skin elements disappear, leaving no pigmentation and peeling. Adults tolerate rubella more severely: the temperature can reach 39 ° C, severe headaches and myalgia, pronounced catarrhs of the nasal mucosa and conjunctiva are possible. The greatest danger is the infection of the fetus during pregnancy - in this case, the formation of multiple defects (cataracts, heart defects, microcephaly and deafness) is observed. The virus is unstable in the external environment, it dies when exposed to physical and chemical factors. Laboratory diagnostics: 1) isolation of the pathogen in human embryonic cell cultures; 2) serological diagnostics (RSK, RTGA) by ELISA and RIA, RN. Treatment: 1) there are no means of etiotropic therapy; 2) pregnant women who have been in contact with the patient are prophylactically injected with a specific immunoglobulin. Specific prophylaxis: live attenuated vaccine; immunization of women of childbearing age should be carried out only in the absence of pregnancy. LECTURE No. 25. Enteroviral infections 1. Polio virus Belongs to the family Picornaviridae, a genus of enteroviruses. They are relatively small viruses with icosahedral symmetry. The average size of viral particles is 22-30 nm. Resistant to the action of fatty solvents. The genome is formed by an unsegmented +RNA molecule. The extracted RNA remains infective even after the removal of the protein molecule by the action of proteases. Each viral particle consists of a capsid built of 60 subunits and containing 4 polypeptides of one VPg molecule connected to RNA. Replication takes place in the cytoplasm; reproductive processes usually take no more than a few hours and are resistant to the action of inhibitors of cellular RNA synthesis. The first stage (after deproteinization) is the synthesis of +RNA and viral proteins, which are translated into a single polypeptide thread. The assembly of host cells and the filling of the capsid are also carried out in the cytoplasm. The release of the virus is accompanied by cell lysis. Viruses are acid-resistant and relatively stable at low pH, which allows them to survive in the acidic environment of the stomach, and the lack of an envelope makes them resistant to the action of bile acids. The antigenic structure of polioviruses is stable, only rare serological variations are possible. Pathogens are highly contagious, especially in the presence of a large crowd of people and violations of elementary sanitary rules and hygiene. The main transmission mechanism is fecal-oral. All polioviruses cause poliomyelitis, an acute infection that affects neurons in the medulla oblongata and anterior horns of the spinal cord. The primary breeding site is localized in the epithelium of the mouth, pharynx, small intestine, as well as in the lymphoid tissues of the Pirogov ring and Peyer's patches. Possible secondary penetration of the virus from the epithelium of the mucous membranes into the lymphoid tissues and bloodstream (primary viremia), and then into various organs, excluding the central nervous system. In the presence of serum antigens, further dissemination of the pathogen stops (abortive infection), otherwise secondary viremia develops and the pathogen enters the central nervous system. Neurons of the anterior horns of the spinal cord, medulla oblongata, and pons varolii carry receptors for polioviruses. Laboratory diagnostics: 1) isolation of the pathogen in primary tissue cultures or cell cultures of HeLa, Hep-2, SOC; indication of the pathogen is carried out according to the cytopathic effect and its neutralization with a typical antiserum; 2) serological studies include the determination of antigens in serum and cerebrospinal fluid; detection of high titers of IgM indicates the presence of infection. Treatment: no specific antiviral therapy is available; carry out symptomatic treatment and prevent the development of secondary bacterial infections. Specific prevention: 1) live (attenuated) vaccine; 2) killed viral vaccine. 2. ECHO viruses. Coxsackie viruses They belong to the family Picornaviridae, a genus of enteroviruses. The structure of the virion is the same as that of the polio virus. ECHO viruses are isolated in a special group of intestinal viruses due to the complete absence of pathogenic effects on laboratory animals. Allocate 34 serovars; the separation is based on the properties of the specific antigen of the viral capsid, which is neutralized by type-specific antigens. 12 serotypes are capable of hemagglutination, some serotypes spontaneously elute. There is no group specific antigen. Some type-specific antigens have a certain cross-reactivity. Infection with ECHO viruses occurs by the fecal-oral route, less often by inhalation. As a rule, the causative agent does not disseminate from the focus of the primary infection; less often it spreads hematogenously, and in severe forms it can be isolated from the affected organ. ECHO viruses cause: 1) SARS and fever of unknown origin; 2) aseptic meningitis (occur relatively easily and do not cause complications); 3) ascending paralysis and encephalitis, resembling lesions caused by polioviruses; 4) a feverish state, accompanied by morbilliform rashes. After the disease, humoral type-specific immunity is formed, the duration of which varies within different limits. Laboratory diagnostics: 1) isolation of the pathogen is carried out by infecting monkey kidney cells with material from the cerebrospinal fluid and feces; 2) serodiagnosis - detection of antigens (in paired sera taken at the onset of the disease and at 2-3 weeks); for detection, reactions of PH, RSK and RTGA are used. Treatment and prevention: there are no means of therapy and effective prevention of ECHO-viral infections; treatment of lesions is symptomatic. Coxsackieviruses are typical picornaviruses. According to biological properties, they distinguish: 1) group A viruses. They cause diffuse myositis with inflammation and focal necrosis of striated muscles; 2) viruses of group B. Cause lesions of the central nervous system (focal degeneration, paralysis), necrosis of skeletal muscles and sometimes myocardium, inflammatory lesions of the spleen, etc. Each group includes serovars: group A - 24, group B - 6. The division is based on the properties of the type-specific antigen. Serovars do not contain a group-specific antigen. Some Coxsackieviruses are capable of causing hemagglutination of human erythrocytes. The main transmission mechanisms are fecal-oral and contact (through the discharge of the nasopharynx). The infectious process caused by Coxsackieviruses is accompanied by the synthesis of type-specific antigens found in the serum a week after the onset of the disease. Laboratory diagnostics: 1) infection of cell culture and suckling mice; material - swabs and swabs from the nasopharynx, intestinal contents; 2) hemagglutinating variants are detected using RTGA, which is characterized by type specificity; 3) belonging to serovars is determined in RSK or RN with type-specific antisera. There is no specific prevention. Etiotropic therapy is absent. LECTURE No. 26. HIV (human immunodeficiency virus) 1. Structure HIV belongs to the retrovirus family. The virion has a spherical shape, with a diameter of 100-150 nm. Cubic type of symmetry. The outer (supercapsid) envelope of the virus consists of a bimolecular layer of lipids, which originates from the cell membrane of the host cell. Spikes of two types protrude from it: 1) gp 120 (has a receptor function); 2) gp 41 (has an anchor function). Receptor formations are embedded in this membrane. Under the outer shell is the core of the virus (core), which has the shape of a truncated cone. The gap between the outer viral membrane and the core of the virus is filled with a matrix protein. Inside the core are two identical viral RNA molecules associated with low molecular weight proteins p6 and p7. Each RNA molecule contains nine HIV genes: 1) structural (three genes); 2) regulatory (three genes, they do not encode the structural components of the virus, but, once in the cell, encode the formation of substances that either inhibit the activity of structural genes or activate them); 3) additional (three genes, they contain the information necessary for the production of proteins that control the ability of the virus to infect a cell, replicate and cause disease). There are three groups of structural genes: 1) gag (encode the formation of structural proteins of the core of the virus); 2) pol (direct the synthesis of proteins - viral enzymes); 3) ent (encode the synthesis of envelope proteins gp 120 and gp 41). The ends of each RNA molecule contain a duplicated RNA sequence. These sites act as switches to control the process of viral transcription by interacting with HIV proteins or host cell proteins. In addition to RNA, viral enzymes are also located there: 1) reverse transcriptase; carries out the synthesis of viral DNA from a viral RNA molecule; 2) protease; participates in the "cutting" of viral protein precursors during the maturation of a new viral particle; 3) endonuclease (integrase); inserts viral DNA into the genome of the host cell, resulting in the formation of a provirus. Antigenic properties have: 1) core proteins; 2) envelope glycoproteins. They are characterized by a high level of antigenic variability, which is determined by a high rate of nucleotide substitutions. Intensive antigenic variability of HIV occurs in the body of patients during infection and in virus carriers. It allows the virus to "hide" from specific antibodies and cellular immunity factors, which leads to a chronic infection. In conventional cell cultures, HIV is not cultivated. For cultivation, a culture of T-lymphocytes with a helper function is used. 2. Pathogenesis and immunological disorders In the body, viruses interact with CD-4 receptors, which are located on the surface of immunocompetent cells - lymphocytes, macrophages. The interaction of a virus with a target cell includes four stages: 1) adsorption to CD-4 receptors; 2) cell puncture and endocytosis; 3) deproteinization with the participation of host cell protein kinases; 4) DNA synthesis on an RNA template with the participation of reverse transcriptase. The DNA of the virus is included in the cell genome, then the synthesis of viral components - proteins occurs, then - the self-assembly of the virion and its budding, during which the virus acquires a supercapsid. The interaction of a virus with a cell can be different: 1) the virus can persist in the cell without showing itself in any way, it may lack the synthesis of nucleic acids and proteins; 2) slow reproduction and budding of the virus and infection of new cells; 3) rapid reproduction of the virus in the cell, its death and the release of the virus. Infection begins with the introduction of the virus into the human body. The pathogenesis of HIV infection includes five main periods: 1) the incubation period lasts from infection to the appearance of antibodies and ranges from 7 to 90 days. The virus reproduces exponentially. No symptoms are observed. The person becomes contagious after a week; 2) the stage of primary manifestations is characterized by explosive multiplication of the virus in various cells containing the CD-4 receptor. Seroconversion begins during this period. Clinically, this stage resembles any acute infection: headache, fever, fatigue are observed, there may be diarrhea, the only alarming symptom is an increase in cervical and axillary lymph nodes. This stage lasts 2-4 weeks; 3) latent period. During this period, the virus slows down its replication and enters a state of persistence. The latent period lasts 5-10 years. The only clinical symptom is lymphadenopathy - an increase in almost all lymph nodes. The number of T-helpers decreases in relation to T-suppressors, delayed-type hypersensitivity reactions disappear; 4) AIDS-associated complex (pre-AIDS). The virus begins to multiply intensively in all tissues and organs, replicate explosively with cell damage. T-helpers are most severely damaged, their complete destruction occurs, which leads to deregulation of the entire immune system, immunity (both humoral and cellular) is sharply reduced; 5) AIDS itself. There is a complete lack of immune response. Duration - approximately 1-2 years, secondary infections are the direct cause of death. 3. Epidemiology. Diagnostics. Treatment Sources of the virus are sick and virus carriers. Ways of transmission of the virus: 1) infection through sexual contact; 2) parenteral infection with blood during blood transfusions, medical manipulations, operations; 3) transmission to newborns through the placenta, in the birth canal, during breastfeeding. Infection is possible in hairdressing salons, when using toothbrushes, and applying tattoos. HIV is present in a sick person in all cells where there are CD-4 receptors - these are T-helpers, tissue macrophages, in intestinal cells, mucous membranes, etc. In an infected person, the virus is excreted with all biological fluids: the maximum amount is in the blood and in seminal fluid. The average amount of virus is in the lymph, cerebrospinal fluid, vaginal discharge. Even less virus in the milk of a nursing mother, saliva, tears, sweat. The content of the virus in them is such that it is not enough to cause an infection. The main risk groups are drug addicts, patients with hemophilia, homosexuals, prostitutes. HIV is characterized by low resistance to physical and chemical factors. Heating at 560°C for 30 minutes reduces the infectious titer of the virus by 100 times, and higher temperatures quickly and completely inactivate the virus. Sensitive to detergents and disinfectants. HIV is resistant to desiccation. Its infectivity persists for 4-6 days at room temperature. Not sensitive to UV radiation. Laboratory diagnostics: 1) screening of antibodies against HIV using enzyme immunoassay (from the beginning of the second period until the death of the infected person). If the reaction is positive, it is repeated with another serum and on a more advanced system. Then immunobloding is carried out; 2) HIV-2 diagnosticum (with suspected HIV infection and with negative reactions to HIV-1); 3) infection of T-helper cultures. The virus is detected by cytopathic action, in serological reactions, by reverse transcriptase activity; 4) hybridization tests using virus-specific nucleic probes. Treatment: 1) etiotropic therapy. Use the following drugs: a) azidothymizine (inactivates the reverse transcriptase of the virus); b) a-interferon (prolongs the latent period, suppressing replication); 2) immunostimulation: interleukin-2, interferons and immunoglobulins are administered; 3) treatment of tumors, secondary infections and invasions. Specific prophylaxis has not been developed. A genetically engineered vaccine containing viral surface glycoproteins is being tested. LECTURE No. 27. Viral zoonotic infections 1. Rabies virus Belongs to the family Rhabdoviridae, genus Lyssavirus. Rhabdoviruses are distinguished by their bullet shape, the presence of a shell, and helical symmetry; the genome is made up of RNA. The average size of the virion is 180 ́ 75 nm; one end is rounded, the other is flat; the surface is convex with spherical structures. The core of the virion is symmetrically twisted inside the shell along the longitudinal axis of the particle. The viral envelope consists of a double lipid layer, which includes external surface glycoprotein structures. The membrane is formed by a surface glycoprotein (G) and two non-glycosylated proteins (Ml and M2). The nucleocapsid is complemented by numerous copies of the core protein (NP) and several copies of the viral transcriptase; the latter is formed by large (L) and small (NS) proteins. The replication cycle is realized in the cytoplasm of the cell. The exit of virions from the cell is carried out by budding. Antigenic structure: 1) nucleoprotein - group-specific antigen; 2) glycoprotein of the outer shell - a type-specific antigen responsible for the infectious and hemagglutinating activity of the virus. Rabies is an acute infection of the central nervous system, accompanied by degeneration of neurons in the brain and spinal cord. Mortality for humans in the absence of timely treatment is 100%. The virus enters the human body through damage to the skin, usually through the bites of sick animals. Virus replication takes place in muscle and connective tissues, where it persists for weeks or months. The virus migrates along the axons of peripheral nerves to the basal ganglia and the central nervous system, where it multiplies in cells, resulting in the appearance of cytoplasmic Babes-Negri bodies containing viral nucleocapsids. The virus then migrates back along the centrifugal neurons to various tissues (including the salivary glands). The time for the virus to move along the nerve trunks corresponds to the incubation period of the disease. Its duration can be different: minimal (10-14 days) with a bite in the head and face, and longer (a month or more) with bites in the limbs. The reservoir of the virus in nature are various warm-blooded animals. A person is a dead end in the circulation of the virus, the transmission of the pathogen from person to person is not observed. Diagnostics: 1) intracerebral infection of laboratory mice; 2) cultivation in cell culture of hamster kidneys. Treatment: 1) broad-spectrum antibiotics; 2) specific anti-rabies immunoglobulin; 3) horse anti-rabies serum; 4) anti-rabies vaccine. Specific prophylaxis: rabies vaccine. 2. Flaviviruses The family includes about 50 viruses. They are spherical enveloped viruses with an icosahedral nucleocapsid enclosed in a lipid envelope. The average value is 37-50 nm. The genome is formed by a single-stranded +RNA molecule. RNA retains infectivity after isolation from the virion. During replication, a homogeneous mRNA is formed. The complete flavivirus genome is translated into a single polyprotein, which is subsequently cut by proteolytic enzymes. After maturation, the daughter populations bud from the cellular or intracellular membranes that serve as assembly sites. Antigenic structure: 1) structural proteins (V); responsible for hemagglutination, species specificity and group antigenic relationships; 2) non-structural soluble antigen. Flaviviruses are cultivated in chicken embryos and tissue cultures. The primary reproduction of the virus occurs in macrophages and histiocytes, then in regional lymph nodes. Then the viruses enter the bloodstream, enter the internal organs, nerve cells of the brain, where they reproduce. After the disease, humoral type-specific immunity remains. The flavivirus family includes various representatives that cause the corresponding diseases: 1) yellow fever virus. The reservoir of infection is monkeys, the carrier is mosquitoes. Found in South African countries. The virus enters the bloodstream and then to the regional lymph nodes, where it multiplies. Daughter populations secondarily penetrate into the blood and hematogenously disseminate to the liver, spleen, bone marrow and other organs. Infection of cells leads to the development of inflammatory and necrotic lesions; 2) Dengue fever virus. The reservoir of infection is sick people and monkeys, the carrier is mosquitoes. With the bite of the carrier, the virus enters the bloodstream, replicates in the regional lymph nodes and capillary endothelium, then the daughter populations re-enter the blood, which is accompanied by the phenomena of capillary toxicosis; 3) Japanese encephalitis virus. Pathogen reservoir - wild birds, rodents, cattle, horses and pigs; a person is a dead-end host (in epidemics, transmissible transmission from person to person is possible). Carriers - mosquitoes of the genus Culex. After a bite, the virus enters the bloodstream, and from there - into the central nervous system, lymphocytes and parenchymal organs. The release of daughter populations is accompanied by cell death; 4) tick-borne encephalitis virus. The reservoir and carrier of the virus are ixodid ticks. Additional tank - various animals and birds. After human bites by infected ticks, the pathogen spreads by hematogenous and lymphogenous routes, penetrating into the central nervous system. The virus infects the motor neurons of the anterior horns of the cervical spinal cord, the cerebellum, and the pia mater. For the specific prevention of tick-borne encephalitis, an inactivated vaccine is used. When a tick bites, a specific immunoglobulin is injected. Laboratory diagnostics: 1) isolation of the virus by infection of suckling mice, subsequent identification in RTGA and RSK with sets of immune sera; 2) final identification in the neutralization reaction. Treatment: means of etiotropic therapy are absent. LECTURE No. 28. The causative agents of viral hepatitis 1. Hepatitis A virus Hepatitis A virus belongs to the picornavirus family, the genus Enterovirus. The hepatitis A virus is morphologically similar to other members of the enterovirus genus. The genome is formed by a single-stranded +RNA molecule; it contains three main proteins. It does not have a supercapsid shell. Antigenic structure: has one virus-specific antigen of a protein nature. The virus has a reduced ability to reproduce in cell cultures. The reproduction of the virus is not accompanied by a cytopathic effect. The virus is resistant to physical and chemical factors. The main mechanism of transmission of the hepatitis A virus is fecal-oral. The patient secretes the pathogen within 2-3 weeks before the onset of the icteric stage and 8-10 days after its completion. The virus is pathogenic only for humans. The hepatitis A virus enters the human body with water or food, reproduces in the epithelium of the mucous membrane of the small intestine and regional lymphoid tissues. Then the pathogen enters the bloodstream with the development of short-term viremia. The maximum titers of the virus in the blood are detected at the end of the incubation period and in the preicteric period. At this time, the pathogen is excreted in the faeces. The main target for cytopathogenic action is hepatocytes. Reproduction of the virus in their cytoplasm leads to disruption of intracellular metabolic processes and cell death. The cytopathic effect is enhanced by immune mechanisms, in particular NK cells, the synthesis of which is induced by the virus. The defeat of hepatocytes is accompanied by the development of jaundice and an increase in the level of transaminases. Further, the pathogen with bile enters the intestinal lumen and is excreted with feces, in which there is a high concentration of the virus. Hepatitis A virus causes the development of an acute highly contagious disease, which can occur subclinically or give typical clinical forms. After the transfer of a clinically pronounced or asymptomatic infection, lifelong humoral immunity is formed. Laboratory diagnostics: 1) determination of the content of bile pigments and aminotransferases in serum; 2) cultivation on leukocyte or organ cultures; 3) ELISA and solid-phase RIA method - to detect antibodies (IgM), which appear in the blood serum already at the end of the incubation period and persist for 2-3 months after recovery. From the middle of the icteric period, IgG are produced, which persist for life; 4) molecular genetic methods - detection of RNA virus in PCR. Treatment: no specific antiviral therapy is available, treatment is symptomatic. Specific prophylaxis: killed vaccine based on strain CR 326. 2. Hepatitis B virus Belongs to the Hepadnaviridae family. These are icosahedral, enveloped DNA-containing viruses that cause hepatitis in various animals and humans. The genome forms an incomplete (with a break in one strand) circular double-stranded DNA molecule. The nucleocapsid consists of a primer protein and a DNA polymerase associated with DNA. For efficient replication, the synthesis of virus-induced reverse transcriptase is necessary, since viral DNA is formed on an RNA template; in the dynamics of the process, viral DNA integrates into the DNA of the cell. DNA synthesis and virus assembly are carried out in the cytoplasm of the infected cell. Mature populations are isolated by budding from the cell membrane. Antigenic structure: 1) HBsAg (includes two polypeptide fragments): a) the preS1 polypeptide has pronounced immunogenic properties; the polypeptide obtained by genetic engineering can be used for the preparation of vaccine preparations; b) preS2 polypeptide (a polyglobulin receptor that causes adsorption on hepatocytes; it is able to interact with serum albumin, as a result of which the latter is converted into polyalbumin); 2) HBcorAg (is a nucleoprotein, is represented by the only antigenic type; it is found only in the core of the virus); 3) HBeAg (is cleaved from HBcorAg due to its passage through the membrane of hepatocytes). Infection occurs by injection of infected blood or blood products; through contaminated medical instruments, sexually and intranatally, intrauterine infection is possible. The site of primary viral replication is unknown; reproduction in hepatocytes is observed only 2 weeks after infection. In this case, the replication cycle is not accompanied by the death of hepatocytes. In the second half of the incubation period, the virus is isolated from blood, semen, urine, feces and nasopharyngeal secretions. The pathological process begins after the recognition of virus-induced antigens on the membranes of hepatocytes by immunocompetent cells, i.e., it is caused by immune mechanisms. Clinical manifestations range from asymptomatic and anicteric forms to severe liver degeneration. The course of hepatitis B is more severe, with a gradual onset, a long infectious cycle, a higher mortality rate than with hepatitis A. Chronization of the process is possible. Laboratory diagnostics: 1) detection of viral antigens by immunofluorescent method; material - feces, blood and liver biopsy material; 2) serological studies include the determination of antigens and antibodies using reagents - HBsAg, HBeAg; antigens to HBsAg, HBcorAg, HBeAg and IgM to HBcorAg; 3) determination of DNA polymerase. Treatment: there are no specific drug therapy, treatment is mainly symptomatic. Specific prevention: 1) passive immunization - specific immunoglobulin (HBIg) is administered; 2) active immunization (recombinant vaccines obtained by genetic engineering). Immunization is indicated for all risk groups, including newborns. 3. Other causative agents of viral hepatitis The hepatitis C virus is an RNA virus. Its taxonomic position is currently not precisely defined; it is close to the flavivirus family. It is a spherical particle consisting of a nucleocapsid surrounded by a protein-lipid membrane. The size of the virion is 80 nm. RNA has zones encoding the synthesis of structural and non-structural proteins of the virus. The synthesis of structural proteins is encoded by the C and E zones of the RNA, and the synthesis of non-structural proteins of the virus is encoded by the NS-1, NS-2, NS-3, NS-4 and NS-5 zones of the RNA. The hepatitis C virus is characterized by antigenic variability, there are seven main variants of the virus. The source of infection are patients with acute and chronic hepatitis C and virus carriers. The virus is transmitted parenterally, sexually and from mother to fetus (with peri- and postnatal infection). The predominance of anicteric forms and the frequent transition to the chronic form of the disease are characteristic. The virus is one of the factors in the development of primary hepatocellular carcinoma. Laboratory diagnostics: 1) detection of RNA virus by PCR; 2) determination of antibodies to the virus in ELISA. The hepatitis D virus does not belong to any of the known families of animal viruses. It is a spherical particle with an average diameter of 36 nm. The genome is represented by a single-stranded, cyclic RNA molecule, which forms a rod-shaped unbranched structure. RNA encodes a virus-specific polypeptide - HDAg (nucleocapsid own antigen). The outer shell forms a surface antigen. Hepatitis D RNA virus replication occurs in the nucleus of an infected hepatocyte. Sources of infection - a sick person and a virus carrier. The route of transmission is parenteral. The hepatitis D virus cannot participate in the development of hepatitis infection without simultaneous replication of the hepatitis B virus. This fact determines two possible forms of their interaction: 1) simultaneous infection with viral hepatitis B and D (conversion); 2) infection of the carrier of the hepatitis D virus with the hepatitis B virus (superinfection). With superinfection, rapid damage to the liver parenchyma occurs with massive necrosis. Diagnosis: detection of antibodies to the virus in ELISA. The hepatitis E virus belongs to the Calicinovirus family. This is a spherical RNA virus, 20-30 nm in size. Ways of transmission - water, food, contact is possible. The source of infection is a patient with an acute or chronic form. The clinical picture is close to hepatitis A. Diagnosis: detection of antibodies in ELISA. LECTURE No. 29. Pathogenic protozoa 1. Plasmodium malaria They belong to the genus Plasmodium. There are four types of human parasites: P. vivax - the causative agent of three-day malaria, P. malariae - the causative agent of four-day malaria, P. falciparum - the causative agent of tropical malaria, P. ovale - the causative agent of malaria-ovale. Morphology and physiology. There are two phases of development of malarial plasmodia. 1. Phase of sexual reproduction. Occurs in the body of the final host - a mosquito of the genus Anopheles. It ends with the formation of a large number of sporozoites - long thin mononuclear cells that are concentrated in the salivary glands. When bitten by a mosquito, sporozoites enter the bloodstream of the vertebrate host. 2. Phase of asexual reproduction - schizogony. Carried out in the body of the intermediate host - humans. It proceeds in two stages: 1) exoerythrocytic schizogony. Sporozoites are brought into the liver with blood flow, invade its cells, in which they are transformed into tissue trophozoites, and then into tissue schizonts. As a result of the division of tissue schizonts, tissue merozoites are formed, which are released into the blood; 2) erythrocyte schizogony. Merozoites are introduced into erythrocytes. After the destruction of red blood cells, merozoites enter the bloodstream. Some of the parasites undergo phagocytosis, while others infect new red blood cells, and the cycle repeats. The pathogenesis of the disease: the release of erythrocyte merozoites, malarial pigment, metabolic products of parasites and structural components of erythrocytes into the blood leads to the development of a feverish reaction. It is characterized by a cyclicity corresponding to the cyclicity of erythrocyte schizogony. Foreign plasmodium proteins cause an anaphylactic reaction. When this happens: 1) increased capillary permeability; 2) hyperplasia of the reticuloendothelial elements of the spleen; 3) inhibition of hematopoiesis; 4) the appearance of allergic symptoms (bronchitis, bronchial asthma). IgM and IgG accumulate in the blood. Change of antigens of plasmodiums in the course of an infection is characteristic. Low susceptibility to tropical malaria has been noted in individuals with abnormal S-hemoglobin, since erythrocytes containing such hemoglobin are unsuitable for the development of this parasite. Malaria is seasonal. The prevalence is associated with the presence of specific carriers - mosquitoes of the Anopheles genus. Diagnostics: 1) microscopy of blood smears of the patient, stained by the Romanovsky-Giemsa method; 2) serodiagnosis - immunofluorescence reactions, passive hemagglutination, enzyme immunoassay. Etiotropic therapy: schizocidal action is possessed by chloroquine, amodiaquine; gamontocidal action - pyrimethamine, proguanil, quinocide, primaquine. 2. Toxoplasma Toxoplasmosis is caused by a single species, Toxoplasma gondii. Morphology and physiology. Reproduction with change of hosts. The main host is a cat (oocysts are formed in its intestines), intermediate hosts are birds, mammals, and humans. The route of infection is alimentary (when using thermally poorly processed meat of infected animals). Life cycle stages: 1) endozoites (trophozoites) and cystozoites - extra- and intracellular stages, during which the parasite is in different organs and tissues of intermediate hosts (including humans) and reproduces asexually; 2) merozoites - intra- and extracellular forms parasitizing in the epithelial cells of the intestine of the main host - cats; reproduce by schizogony; 3) micro- and macrogametes - sexual stages of development, formed mainly in the host cat; at the fusion of male and female gametes (micro- and macrogametes, respectively), a zygote appears, which then turns into a resting stage - an oocyst; oocysts are excreted into the external environment with cat feces; 4) sporozoites - an invasive stage formed as a result of sporogony inside the oocyst outside the body of the main host. Endozoites - cells measuring 4-7 by 1,5-2 microns, having the shape of a crescent with a poorly structured cytoplasm. The nucleus is located in the back wall of the cell. Cystozoites of Toxoplasma are localized in cysts, which provides the parasite with the possibility of long-term persistence in the organism of the intermediate host. Cysts are located intracellularly in the brain, striated muscles and other organs of the intermediate host. Endocysts quickly perish in the external environment, remain for a short time in the corpses and excrement of carriers. Cysts are more stable. Pathogenesis: Toxoplasma have a cytopathic effect. They are able to penetrate into the cell nucleus and parasitize in it. Toxoplasma affects the cells of the connective, epithelial, nervous and muscle tissues. They produce a toxin that is involved in the formation of microfoci of necrosis. With the reproduction of endozoites, an inflammatory process occurs. Distinguish: 1) congenital toxoplasmosis (from mother to fetus) - affects the central nervous system, eyes; 2) acquired toxoplasmosis - various clinical forms. In the blood - IgM and IgG. The formation of a delayed-type hypersensitivity reaction is characteristic. Diagnostics: 1) serological methods - RSK, RPHA, indirect fluorescence, enzyme immunoassay; 2) isolation on laboratory animals. Treatment: chloroquine, amodiaquine have a schizocidal effect, pyrimethamine, proguanil, quinocide, primaquine have a gamontocidal effect. 3. Giardia They belong to the genus Lamblia, which includes more than 100 species. A specific human parasite is the species L. intestinalis, which lives in the upper sections of the small intestine. Morphology and physiology. The length of the parasite is 15 microns, the width is 7-8 microns. The shape of the cell is pear-shaped, pointed towards the posterior end. In the anterior part there is a suction disk, with the help of which Giardia is tightly attached to the epithelial cells of the small intestine. In the lower intestines, the vegetative stages of Giardia can pass into the cyst stage. Giardia are cultivated on nutrient media containing extracts of yeast-like fungi. Pathogenesis. Moderate invasion of the small intestine is usually not painful. More pronounced infection with these parasites can lead to severe intestinal disorders. Penetrating through the bile duct from the duodenum to the gallbladder, Giardia can cause chronic cholecystitis. Pathological phenomena usually manifest themselves with a massive infection with lamblia of persons with weakened body resistance. They are more common in children than in adults. Diagnostics. Microscopic examination of native and Lugol-treated preparations prepared from feces and duodenal contents. Treatment: apply quinacrine and aminoquinol. List of used literature 1. Gusev M. V., Mineeva L. A. Microbiology. M.: Medicine, 2003. 2. Elinov N. P. Chemical microbiology. M.: Medicine, 1989. 3. Podkolzina V. A., Sedov A. A. Medical microbiology. Lecture notes. M.: Prior, 2005. 4. Shub G. M. Fundamentals of medical bacteriology, virology and immunology. Tutorial. Saratov, 2001. Author: Tkachenko K.V.
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