Hemolysins of vibrio cholerae and other vibrio species

Bacteria of the genus Vibrio are normal habitants of the aquatic environment. These species can be classified into two groups according to the types of diseases they cause: One group causes gastrointestinal infections and the other extraintestinal infections. Although the most important pathogenic factor of Vibrio cholerae O1/O139 is cholera enterotoxin (CT), a hemolysin (El Tor hemolysin) produced by biovar eltor is also reported to cause diarrhea. A thermostable direct hemolysin (TDH) produced by Vibrio parahaemolyticus is also believed to be a major pathogenic component of the species. This chapter offers a review of recent information on hemolysins of pathogenic vibrios with special reference to the two representatives. Hemolysins produced by pathogenic vibrio are classified into three groups, namely the VCC group, TDH group, and others. This review focused on four hemolysins: VCC, Vp-TDH, W H and VMH, which have been extensively studied. All four are poreforming toxins, but their precise mechanism of action remains to be investigated. VCC, Vp-TDH, and VMH have activity that causes diarrhea, the major symptom of infection of these vibrios, although VCC is no more than a supplemental factor of CT and VMH is only one of the many enterotoxic factors.