Infectious diseases. Pneumococcal infection. Etiology. Epidemiology. Pathogenesis. Pathomorphology (most important)

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Infectious diseases. Pneumococcal infection. Etiology. Epidemiology. Pathogenesis. Pathomorphology (most important)

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13. Pneumococcal infection. Etiology. Epidemiology. Pathogenesis. Pathomorphology

Pneumococci (Streptococcus pneumoniae) are common inhabitants of the human upper respiratory tract, but under certain conditions they can become pathogens of infectious diseases that are clinically manifested by purulent-inflammatory changes in various organs and systems, more often in the lungs - by the type of croupous pneumonia and in the central nervous system - by type of purulent meningitis.

Etiology. Pneumococci are Gram-positive, lanceolate, capsule-forming diplococci that can be found as single cocci or in chains. For humans, only smooth capsular strains of pneumococci are pathogenic. Somatic antigens of pneumococcus have been isolated, antibodies to which cause an insignificant part of immunity. Antibodies to capsular antigens are of primary importance in protective reactions. Pneumococci produce hemolytic toxin, pneumolysin and toxic neuraminidase. When the pathogen is destroyed, endotoxin is released, causing hemorrhages on the skin and mucous membranes.

Epidemiology. Many healthy individuals are carriers of pneumococci. Serovars that do not have pronounced virulent properties predominate among the carriers. The development of the disease in these cases is possible with a sharp decrease in the immunological reactivity of the body.

The source of infection is a person - a patient or a carrier of pneumococci. The infection is transmitted by airborne droplets.

Pathogenesis and pathomorphology. Pneumococci must be considered as potential pathogens. Nonspecific mechanisms of local immunity, including the presence of other microorganisms in the nasopharynx, significantly limit the reproduction of pneumococcus. Pneumococcal diseases often develop after a viral infection of the respiratory tract, in which the ciliated epithelium is affected and its activity is reduced, and the activity of alveolar macrophages is also suppressed. The secret of the respiratory tract can delay the process of phagocytosis.

In the tissues, pneumococci begin to multiply and spread with the flow of lymph and blood or through contact from the site of infection. The severity of the disease is determined by the virulence of the pathogen, its quantity, especially in bacteremia, and the state of reactivity of the macroorganism. The most unfavorable prognosis is with massive bacteremia and a high concentration of capsular polysaccharide in the blood. A severe progressive form of the disease develops in most patients with antigenemia, despite ongoing intensive antibiotic therapy.

The spread of infection in the tissues of patients is enhanced by the action of the antiphagocytic substance of the soluble capsular antigen of pneumococci. An important role is played by the factor contributing to the development of edema. Subsequently, the number of macrophages in the exudate increases, and phagocytosis of pneumococci increases. The processes of resolving pneumonia are completed in 7-10 days.

Author: Pavlova N.V.

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The pleasure of new words 08.11.2014

Remembering new words, we experience pleasure, say researchers from the Otto von Guericke University (Germany) and the University of Barcelona (Spain). The experiment of Pablo Ripolles and his colleagues involved more than thirty adult volunteers who had to understand the meaning of a word from two suggestive sentences. For example, if one sentence reads "The whole family dine at table" and the second sentence reads "Table is made of wood", then from the context we can understand that table means table.

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