Violet Red Bile Agar

Violet Red Bile Agar (VRBA) is a selective and differential culture medium formulated for the enumeration of coliform bacteria in food, dairy, and water samples. The medium contains crystal violet and bile salts as selective inhibitors against Gram-positive organisms, while lactose fermentation by coliforms produces acid that reacts with the neutral red indicator, forming characteristic purple-red colonies. The rapid and reliable differentiation of lactose-fermenting enteric bacteria makes Violet Red Bile Agar a standard method in food safety testing and environmental microbiology.