EXOTOXINS

 Exotoxins

Exotoxins are a group of soluble proteins that are secreted by the bacterium, enter host cells, and catalyze the covalent modification of a host cell component(s) to alter the host cell physiology. Both Gram negative and Gram-positive bacteria produce exotoxins. 

A specific bacterial pathogen may produce a single exotoxin or multiple exotoxins.

Each exotoxin possesses a unique mechanism of action, which is responsible for the elicitation of a unique pathology. 

Thus, the role of exotoxins in bacterial pathogenesis is unique to each exotoxin. Corynebacterium diphtheriae produces diphtheria toxin, which is responsible for the systemic pathology associated with diphtheria, whereas Vibrio cholerae produces cholera toxin, which is responsible for the diarrheal pathology associated with cholera

Exotoxins vary in their cytotoxic potency, with the clostridial neurotoxins being the most potent exotoxins of humans. Exotoxins also vary with respect to the host that can be intoxicated.

Exotoxin A (ETA) of Pseudomonas aeruginosa can intoxicate cells from numerous species, whereas other toxins, such as diphtheria toxin, are more restricted in the species that can be intoxicated. Some bacterial toxins, such as pertussis toxin, can intoxicate numerous cell types, whereas other toxins, such as the clostridial neurotoxins, show a specific tropism and intoxicate only cells of neuronal origin.

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