Causes of pneumococcal infection

Causes of pneumococcal infection

Pneumococcus (Streptococcus pneumonie) - Gram-positive diplococcus oval or lanceolate, surrounded by a polysaccharide capsule. Refers to the genus Streptococcus family Streptococcaceae. Depending on the structure of the capsular antigen, 85 serotypes are isolated. The main pathogenicity factors are the capsule, the suppressing phagocytosis, and the teichoic acid of the cell wall reacting with CRP. Pneumococcus grows on nutrient media containing protein, in the environment is stable, sensitive to the action of disinfectants. Pneumococcus is sensitive to antibacterial drugs of various groups.

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Pathogenesis of pneumococcal infection

Depends on the clinical form of pneumococcal infection. In the development of manifest forms of the disease, the virulence of the pathogen strain and the decrease in the resistance of the mucous membrane of the upper respiratory tract, nonspecific and specific protective factors are important. Due to the presence of a capsule, pneumococcus is protected from phagocytosis. Teichoic acids activate the complementary cascade and initiate the release of mediators of the acute phase of inflammation, which leads to tissue damage. From the upper respiratory tract causative agent on contact penetrates into the paranasal sinuses, along the eustachian tube - into the middle ear; on contact and lymphogenically from the middle ear, the main, lattice and frontal sinuses reaches the membranes and substance of the brain. It is also possible hematogenous spread of pneumococcus with the development of pneumonia, septicemia (pneumococcemia), endocarditis and primary meningitis.

Epidemiology of pneumococcal infection

The source of pneumococcal infection is healthy carriers and patients with pneumonia, as well as pneumococcal rhinitis. The main transmission path is air-drop, contact is possible. The susceptibility is low. Pneumococcal infections are widespread (80% of community-acquired pneumonia, otitis media, sinusitis, and 30% of bacterial meningitis). When infection usually develops a healthy carrier or rhinitis. The duration of a healthy carrier in children 3-4 weeks, in adults - up to 2 weeks. Carrier frequency is higher in children's groups, in winter is higher than in summer. In children, serotypes 6, 14.19 and 23 are more often detected, in adults - serotypes 1, 3, 4, 7-9 and 12. As a result of carriage, type-specific immunity is formed. Duration and intensity of it are not established.

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