Toxins of Vibrio Parahæmolyticus and Æromonas Hydrophila

Abstract

The related species V. parahæmolyticus and A. hydrophila produce several extracellular toxins and enzymes some of which are potential virulence factors. The thermostable direct hemolysin of V. parahæmolyticus (Kanagawa-hemolysin) is produced by the majority of strains isolated from human patients but its role in the pathogenesis of gastroenteritis is not clear. This hemolysin is cytotoxic to a wide variety of mammalian cells, it is lethal to mice and the cell membrane is a glycoconjugate. These properties are shared with the AEromonas beta-hemolysin (ærolysin) and the two hemolysins may be related. A. hydrophila produces an enterotoxin which increases the intracellular cAMP content of intestinal cells, induces steroidogenesis in adrenal Y1 cells, and fullfils the criteria for a cytotonic enterotoxin but appears not to be antigenically related to cholera toxin. There is so far no conclusive evidence for the production of a similar enterotoxin in strains of V. parahæmolyticus. Strains of both species produce phospholipases and proteases. The greater tendency of A. hydrophila to cause extraintestinal and systemic disease may reside in the production of extracellular enzymes.