Violet Red Bile Agar (VRBA)

Violet Red Bile Agar is used for the enumeration of coliforms in food and dairy products in a laboratory setting. Violet Red Bile Agar is not intended for use in the diagnosis of disease or other conditions in humans and conforms to American Public Health Association (APHA).

The coliform group of bacteria includes aerobic and facultative anaerobic, gram-negative, non-spore forming bacilli. Coliforms ferment lactose and form acid and gas at 35°C within 48 hours. Members of Enterobacteriaceae comprise the majority of the group, but other lactose fermenting organisms may also be included.

Procedures to detect, enumerate, and presumptively identify coliforms are used in testing foods and dairy products. One method for performing the presumptive test for coliforms uses Violet Red Bile Agar, (VRBA). If typical coliform colonies appear, they are tested further to confirm their identification as coliforms. Coliform colonies lower the pH of the medium, subsequently causing their colonies to look red (Neutral Red Dye) and to precipitate the bile salts.