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Causes of Haemophilus influenzae infection in children
Last reviewed: 04.07.2025
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Causes of Haemophilus influenzae infection
H. influenzae are gram-negative pleomorphic rod-shaped or coccoid cells measuring (0.2-0.3) x (0.5-2) µm. They are located in smears singly or in pairs, and sometimes in the form of short chains and groups. On dense media they form small (up to 1 mm in diameter) round colorless colonies. Microorganisms are immobile, do not form spores, but it is possible to form capsular forms, which are associated with pathogenic properties. The pathogen produces endotoxin, the carrier of which is considered to be capsular polysaccharides. According to the antigen structure, 6 serotypes are distinguished (a, b, c, d, e, f). Type b is of leading importance in the development of various pathological conditions. The microorganism is pathogenic only for humans,
[ Pathogenesis of hemophilic infection
The disease occurs with a combination of early age and a decrease in local protection and general specific reactivity. Genetic predisposition, the formation of an epidemic clone of the pathogen, its combination with other microorganisms (mixed infection) are also important.
In a child's body, the pathogen is usually localized in the mucous membranes of the nasopharynx and respiratory tract, located both extra- and intracellularly. Endogenous infection occurs in conditions of total depression of cellular and humoral immunity, usually manifesting itself as a complication of acute respiratory viral infection or another viral or bacterial infection.
In case of exogenous infection, bacteria enter the mucous membranes of the respiratory tract, causing an acute inflammatory process in the form of bronchitis, pneumonia, otitis, tonsillitis, etc. It is also possible to form abscesses, phlegmon, purulent meningitis, sepsis. In severe cases, H. influenzae type b is usually isolated, other types are detected almost exclusively in mild forms of the disease.