Violet Red Bile Glucose Agar (VRBGA)

Violet Red Bile Glucose Agar is used for the enumeration of Enterobacteriaceae in foods. Violet Red Bile Glucose Agar conforms to Harmonized USP/EP/JP requirements and is not intended for use in the diagnosis of disease or other conditions in humans. A medium recommended by the Harmonized USP/EP/JP for isolation and identification of bile-tolerant Gram-negative bacteria from non-sterile products. Conforms to Harmonized USP/EP/JP performance specification. Yeast extract provides vitamins and gelatin serves as source of carbon and nitrogen. Glucose is a fermentable carbohydrate and sodium chloride maintains the osmotic balance. Bile salts and crystal violet act as selective agents inhibiting many Gram-positive bacteria. The formulation is a modification of Violet Red Bile Agar by Mossel which substitutes lactose for glucose. Enterobacteriaceae, such as Escherichia coli and Salmonella spp., are able to ferment glucose. This produces acid which results in a pH drop indicated by neutral red resulting in pink colonies. Enough acid production will cause the precipitation of bile salts resulting in a bile precipitate or halo around glucose fermenting bacteria. Non-glucose fermenting bile tolerant bacteria such as Pseudomonas aeruginosa grow but remain colorless with no bile precipitate. According to the Harmonized USP/EP/JP, Enterobacteria Enrichment Broth-Mossel is used as a selective enrichment broth, with subculture performed onto Violet Red Bile Glucose Agar (VRBGA).