Vibrio Aeromonas and Plesiomonas

■ Vibrio cholerae is the most important species in this group from a medical point of view. Cholera vibrios are Gram-negative, comma-shaped, monotri-chously flagellated rods. They show alkali tolerance (pH 9), which is useful for selective culturing of V. cholerae in alkaline peptone water. The primary cholera pathogen is serovar O:1. NonO:1 strains (e.g., O:139) cause the typical clinical picture in rare cases. O:1 vibrios are further subdivided into the bio-vars cholerae and eltor. The disease develops when the pathogens enter the intestinal tract with food or drinking water in large numbers (-108). The vibrios multiply in the proximal small intestine and produce an enterotoxin. This toxin stimulates a series of reactions in enterocytes, the end result of which is increased transport of electrolytes out of the enterocytes, whereby water is also lost passively. Massive watery diarrhea (up to 20 l/day) results in exsiccosis. The initial therapeutic focus is thus on replacement of lost electrolytes and water. Cholera occurs only in humans. Preventive measures concentrate on protection from exposure to the organism. A killed whole cell vaccine and an attenuated live vaccine are available. They provide only a moderate degree of protection over a period of only six months. International healthcare sources report an incubation period of five days. ■

The bacteria in these groups are Gram-negative rods with a comma or spiral shape. Their natural habitat is in most cases damp biotopes including the ocean. Some of them cause infections in fish (e.g., Aeromonas salmonicida). By far the most important species in terms of human medicine is Vibrio cholerae.

Vibrio, Aeromonas, and Plesiomonas 297

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