TCBS Agar , 250g

Description: 

TCBS Agar was developed by Kobayashi e t al (1), who modified the selective medium of Nakanishi (2). Although this medium was originally designed for the isolation of V.cholerae and V. parahaemolyticus , most Vibrios grow to healthy large colonies with many different colonial morphologies. TCBS Agar is also recommended by APHA for the selective isolation of V. cholerae and V.parahaemolyticus (3,4). Enrichment in Alkaline Peptone Water (M618), followed by isolation on TCBS Agar is routinely used for isolation of V.cholerae (5-7). Proteose peptone and yeast extract provide nitrogenous compounds, vitamin B complex and other essential growth nutrients. Oxgall, a derivative of bile salts and sodium citrate inhibit gram-positive bacteria and coliforms (8).

Sodium thiosulphate serves as a good source of sulphur, which in combination with ferric citrate detects the production of hydrogen sulphide. For the metabolism of Vibrios , sucrose is added as a fermentable carbohydrate. Vibrio that is able to utilize sucrose will from yellow colonies. Bromothymol bl ue and thymol blue are the pH indicators. The alkaline pH of the medium improves the recovery of V.cholerae . Strains of V. cholerae produce yellow colonies on TCBS Agar because of fermentation of sucrose. V.alginolyticus also produce yellow colonies. V.pa rahaemolyticus is a sucrose non-fermenting organism and therefore produces blue-green colonies, as does V.vulnificus .

Proteus species that are sucrose-fermenters may form yellow colonies (9). TCBS Agar is not a suitable medium for oxidase testing of Vibri o species (10). A few strains of V. cholerae may appear green or colourless on TCBS Agar due to delayed sucrose fermentation (9). TCBS Agar is highly selective for Vibrio species. However, occasional isolates of Pseudomonas and Aeromonas may also form blue green colonies on TCBS Agar (9). Any H2S negative colony of TCBS Agar can be considered presumptive positive for Vibrio . The medium should be inoculated heavily with faecal specimens because growth of few species may be inhibited on the medium due to fer mentation of sucrose and accumulation of acids. 

Specification: 

250g