TCBS Agar (Thiosulfate-Citrate-Bile Salts-Sucrose Agar) is a selective medium for isolating Vibrio cholerae and Vibrio parahaemolyticus from clinical and environmental samples. Its alkaline pH promotes Vibrio growth while inhibiting other bacteria. Sucrose fermentation by V. cholerae produces yellow colonies. V. parahaemolyticus (non-sucrose fermenter) forms blue-green colonies.