V. cholerae was first isolated in pure culture in 1883 by Robert Koch. Humans are the only natural host for this organisms and there have been 6 great pandemics of cholera. The genus Vibrio is composed of Gram negative, curved rods that are motile by means of a single polar flagellum. The El Tor biotype produces less toxin but colonizes better and is more resistant to environmental factors. The acid sensitivity of V. cholerae means that a large dose is required to produced disease.
Cholera is a disease of the small intestine, unlike most other enteric illnesses.
The bacteria penetrate the mucus layer and adhere to the mucosal cells where they subsequently produce toxin. The potent enterotoxin choleragen is well defined. Binding via B leads to penetration of the A1 peptide, which enzymatically transfers ADP-ribose from NAD to a GTP regulatory protein. Gastric acidity plays an important role in preventing cholera infection. Also, genetic factors may be important since the toxin must bind to specific cellular receptors in order to function.