What is tcbs agar?

TCBS agar (Thiosulfate Citrate Bile Salts Sucrose agar) is a selective and differential agar medium used in the isolation and identification of Vibrio spp., especially Vibrio cholerae, a bacterium that causes cholera.

The medium contains thiosulfate, citrate, bile salts, and sucrose, which selectively inhibit the growth of Gram-positive bacteria and many Gram-negative bacteria, while allowing for the growth of Vibrio species. The sucrose in the medium also helps in the differentiation of sucrose-fermenting and non-fermenting bacteria.

Colonies of Vibrio species on TCBS agar appear yellow due to the fermentation of sucrose, while other non-sucrose fermenting bacteria may appear green or blue-green. The presence of bile salts in the medium helps in the differentiation of Vibrio cholerae, which produces yellow colonies, from other Vibrio species that produce green colonies.

Overall, TCBS agar is a useful medium for the selective isolation and differentiation of Vibrio species from clinical and environmental samples, particularly in the diagnosis of cholera.