For isolation of coliform and lactose fermenting enteric bacteria. MacCONKEY AGAR (W/ CV, NaCl, 0.15% BILE SALTS & 1% LACTOSE) (VEG.) is used for isolation of coliforms and lactose fermenting enteric bacteria. The medium can be used for the direct plating of water samples for coliform bacilli, for the examination of food samples for food poisoning organisms and for the isolation of Salmonella and Shigella species in cheese. USP recommends this medium for use in the performance of Microbial Limit Tests. The medium consists of Vegetable extract, Peptic digest of Gelatin and Veg. Ceh enzymatic hydrolysate as the sources of nitrogen, carbon and amino acids for the growth of organinsms. Sodium chloride maintains the osmotic balance. Medium incorporated with two types of dyes, Crystal violet & Neutral red. Many of the gram-positive bacteria are inhibited by the action of Synthetic detergent & Crystal violet. Lactose is a fermentable sugar. Lactose fermenting bacteria grow as red or pink and may be surrounded by a zone of acid precipitated bile. The red colour is due to production of acid from lactose, absorption of neutral red and a subsequent colour change of the dye when the pH of medium falls below 6.8. Lactose non-fermenting strains, such as Salmonella are colourless and transparent and typically do not alter appearance of the medium. E.coli may appear as small, lactose fermenting colonies after incubation at room temperature with good growth of colonies having pink to red in colour.