Violet Red Bile Glucose Agar Violet Red Bile Glucose Agar is a selective medium for the isolation and enumeration of enterobacteriacae in food products. It is a modification of the original Violet Red Bile Agar (PP1150) with the Lactose being replaced with Glucose. As all members of the enterobacteriacae ferment Glucose it allows for a wider range of organisms to be detected. The medium is made selective by the inclusion of Bile Salts and Crystal Violet to inhibit gram-positive and other non-enteric organisms.