TCBS AGAR (VIBRIO SELECTIVE AGAR) ishighly selective for the isolation of Vibrio choleraeandV.parahaemolyticusfrom stool specimens, and specified in standard methods for food testing. This highly selective medium meets the nutritional requirements of Vibriosp., and allows competing with intestinal flora. Vibriospp. is able to grow in media containing increased salt concentrations. Vibrio spp. are natural inhabitants of water. Special peptone and Yeast extractarethe source of vitamins, carbon, nitrogen and amino acids in the medium. Sodium thiosulphate serves as a sulphur source and, in combination with Ferric citrate, detects hydrogen sulphide production. Sucrose is included as a fermentable carbohydrate for the metabolism of Vibrios. Inhibition of gram-positive bacteria is achived by the incorporation of Oxgall, which is a naturally occurring substance containing a mixture of bile salts, and Sodium cholate, a pure bile salt. Oxgalland cholate suppress primarily enterococci. The alkaline pH of the medium enhances the recovery of V. cholera becausethis organism is sensitive to acid environments. Thymol blue and Bromothymol blue are included as indicators of pH changes. Sodium citrate and Sodium thiosulpahte are the selective agents, providing an alkaline pH to inhibit gram-positive organims and suppress coliforms. Agar is the solidifying agent. TCBS agar deeps (pour tubes) are provided in a 20 ml fill so that the medium may be liquefied and poured into a petri plates. This provides a convenient source of medium with a longer shelf -life than pre-poured plated media.