MacConkey Agar II w/o CV

MacConkey Agar II w/o CV is recommended for selective isolation and differentiation of lactose fermenting and lactose non-fermenting enteric bacteria. It is the selective and differential medium specially designed to improve the inhibition of swarming Proteus species and to achieve more definitive differentiation of lactose fermenters. Differentiation of enteric microorganisms is achieved by combination of lactose and neutral red indicator. Gram-negative bacteria are differentiated by their ability to ferment lactose. Lactose fermenting strains such as Enterococic grow as red or pink colonies. 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. Escherichia coli ferments lactose and their colony is pink to red with bile precipite. Lactose non-fermenting strains, such as Shigella and Salmonella are colourless and transparent and typically do not alter appearance of the medium.