It is recommended by BIS committee under specification IS 5401 (Part 1):2002.
VIOLET RED BILE AGAR is used for the isolation and confirmation of coli - aerogenes in water, milk and other dairy products. Peptone and Yeast extract are a source of nitrogen, sulphur, carbon, vitamins and minerals. Bile salts and crystal violet are the inhibitors of gram-positive microorganisms. Lactose is the fermentable carbohydrate. Neutral red change to red-purple due to the building of acid during fermentation which change the pH. Sodium chloride is for the osmotic balance. It relies on the use of the selective inhibitory components crystals violet and bile salts and the indicator system lactose, and neutral red. Other gram-negative bacteria can be suppressed by incubation at temperature over 42°C for 18 hours or anaerobic incubation. Agar is the solidifying agent. Lactose fermenting coliforms give red colonies with precipitation of bile salts. Lactose non-fermenters and late lactose fermenters produce pale colonies.
The Enterobacteriaceae group includes lactose-fermenting coliforms bacteria and non-lactose fermenting species like Salmonella and Shigella.