Violet Red Bile Agar
Violet Red Bile Agar is used for the detection and determination of coliforms in food, milk, water, and other sanitary materials. It is a selective medium which detects the growth of lactose-fermenting coliforms. Neutral Red within this formulation acts as a pH indicator, while Crystal Violet and Bile Salts inhibit the growth of Gram-positive microorganisms. Coliform colonies lower the pH of the medium, subsequently causing their colonies to look red (Neutral Red Dye) and to precipitate the bile salts. Pancreatic Digest of Gelatin and Yeast Extract provide nitrogen, vitamins, minerals, and amino acids essential for bacterial growth. Agar is the gelifying agent. Lactose is the fermentable carbohydrates and Sodium Chloride supplies essential electrolytes and maintains the osmotic equilibrium.