Genus Vibrio
General: Comprised of >60 species of curved rods, 10 of which cause human infections. Most have a single polar flagellum. They have a range of pili, important for virulence. All have lipid A (endotoxin) core polysaccharide, with variable O polysaccharide side chains, in their cell walls. Serogroups are defined by their O polysaccharide variant; there are 140 V. cholerae (O1 - O140), 7 V. vulnificus, and 13 V. parahaemolyticus serogroups. (View individual species for details.) Plasmids are common.
Clinical:
- Normal: Estuarine and marine environments, including contaminated waters of high salinity. Associated with chitinous shellfish. Some humans can be asymptomatic carriers, usually in endemic areas.
- Abnormal: Gastrointestinal, with or without cholera toxin. Pathogenicity is enhanced by toxin co-regulated pili and chemotaxis proteins, which combine to prevent organisms from being flushed out with diarrhea; also zonnula occludens toxin, accessory cholera enterotoxin, thermostable direct hemolysin (TDH, or Kanagawa hemolysin), and/or a capsule. Cause a profuse watery diarrhea (~1L/hr).
Resistance:
Growth characteristics: Grow on a variety of simple media over a broad temperature range (14 ~ 40C) and pH range (6.5 ~ 9.0), though are susceptible to normal stomach pH unless there is a high innoculum. V. cholerae can grow without salt, while most species pathogenic in humans require it (are halophiles).
Common/important pathogens: