Vibrio species, like many other gram-negative bacteria, grow in the presence of relatively high levels of bile salts. They are facultatively anaerobic and grow best in alkaline conditions. Isolation is facilitated by the use of media formulated with an alkaline pH due to the tolerance of this condition by Vibrio species. Media can be made selective for Vibrios by adding appropriate selective agents. The main agents employed are bile salts, teepol, tellurite and polymyxin B and E (Colistin) (1). Vibrio Agar is a selective medium for the isolation of Vibrio cholerae, Vibrio parahaemolyticus and other Vibrios (2). Tryptone, proteose peptone, yeast extract provide nitrogenous, carbonaceous compounds, sulphur, vitamin B complex and other essential growth nutrients. Sodium citrate, sodium deoxycholate and bile inhibit gram-positive organisms and coliforms. Sucrose is the fermentable carbohydrate. Sucrose fermentative bacteria such as V. cholerae and V. alginolyticus form blue colonies due to the indicator china blue.V. parahaemolyticus forms slightly reddish and translucent colonies. Sodium thiosulphate in combination with ferric citrate detects H2S production. Thiosulphate also acts as a sulphur source. Alkaline pH of this medium helps in recovery of V. cholerae. China blue and cresol red are the pH.
Application: Vibrio Agar is used for Selective Cultivation of Vibrio Species