V. cholerae

Genus: Vibrio (comma bacillus)The genus vibrio comprises members pathogenic to man, others are pathogenic for animals or insects and many are commensals or saprophytic particularly in water. The medically important vibrios:1. V. cholerae serotype 01, cause cholera•Biotype Classic•Biotype El-Tor2. V. cholerae serotype 0139 bengal, cause cholera3. V. cholerae serotype non-01, cause cholera-like diarrhea and rarely extra-intestinal infections4. V. parahaemolyticus, cause gastroenteritis.

Microscopical appearance: •Gram -ve, non-sporing, non-capsulated.•Small rods, slightly curved (comma shaped). Often lose their curved appearance on artificial cultivation.•Actively motile by a single polar flagellum.

Cultural characteristics: •Aerobic•Grows on ordinary media.•Grows best in an alkaline pH (8.5-9.5).•On agar media colonies are convex, smooth, round, and opaque.•On MacConkey agar colonies are colorless (late lactose fermenter).•On TCBS (Thiosulfate-citrate-bile-sucrose) agar a selective and differential medium for the genus Vibrio.V. cholerae colonies are large and yellow due to sucrose fermentation.V. parahaemolyticus grows on TCBS without fermenting sucrose. Thus the color of the colonies remain green.


Biochemical reactions: • Oxidase +ve• Catalase +ve• Indole +ve• Voges-proskauer test:V. cholerae biotype Classical –ve, V. cholerae biotype El-Tor +ve• Growth in broth containing 8%NaCl:V.cholerae–ve, V. parahaemolyticus +ve (halophile)