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Causes and pathogenesis of diphtheria
Last reviewed: 23.04.2024
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Cause
Causes of diphtheria
Diphtheria causative agent - Corynebacterium diphtheriae - thin, slightly curved stick with clavate thickening at the ends, fixed; spores, capsules and flagella do not form, Gram-positive. By the ability to form a toxin of corynebacteria diphtheria is divided into toxigenic and non-toxic.
In addition to toxin, corynebacteria diphtheria in the process of vital activity produce neuraminidase, hyaluronidase, hemolysin, necrotizing and diffuse factors that can cause necrosis and dilution of the main substance of connective tissue.
Diphtheria toxin - a potent bacterial exotoxin - determines both general and local clinical manifestations of the disease. Toxigenicity is genetically determined. Non-toxic corynebacteria diphtheria disease does not cause.
According to the cultural and morphological features, all corynebacteria diphtheria are divided into 3 variants: gravis, mitis, intermedius. There is no direct correlation between the severity of the disease and the variant of the corynebacterium. Each variant contains both toxigenic and nontoxigenic strains. Toxogenic corynebacteria of all variants produce an identical toxin.
[Pathogenesis
Pathogenesis of diphtheria
The entrance gate of the infection is the mucous membranes of the oropharynx, nose, larynx, less often - the mucous membrane of the eyes and genital organs, as well as damaged skin, wound or burn surface, diaper rash, unhealed umbilical wound. At the entrance gate of the corynebacterium, diphtheria multiplies and releases exotoxin.
There is sweat exudate, rich in fibrinogen, and its transformation into fibrin under the influence of thrombokinase, released by necrosis of epithelial cells. Fibrinous film is formed - a characteristic sign of diphtheria.