A medium recommended by the Harmonised European Pharmacopoeia for isolation and identification of Escherichia coli from non-sterile pharmaceutical products.
Conforms to USP/EP/JP performance specification. Gelatin serves as source of carbon and nitrogen. Lactose 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. Escherichia coli can ferment lactose to produce acid which results in a pH drop. This is 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 lactose fermenting bacteria. Non-lactose fermenting bacteria such as Salmonella spp. grow but remain colourless with no bile precipitate. According to the Harmonised European Pharmacopoeia, MacConkey Broth is used as a selective enrichment broth, with subculture performed onto MacConkey Agar.