MacConkey Broth is used for the detection of coliform bacteria in milk and water. Conforms to Harmonized USP/EP/JP Requirements and is not intended for use in the diagnosis of disease or other conditions in humans. A medium recommended by the Harmonized USP/EP/JP for the selective enrichment of Escherichia coli from non-sterile samples. Conforms to Harmonized USP/EP/JP performance specification. Gelatin peptone provides a source of nitrogen, while lactose is a fermentable carbohydrate. Ox bile acts a selective agent inhibiting most Gram-positive organisms and bromocresol purple acts as a pH indicator. A color change from purple to yellow indicates growth of a bile tolerant, lactose fermenting organism such as Escherichia coli. According to the Harmonized USP/EP/JP, MacConkey Broth is used as a selective enrichment broth, with subculture performed onto MacConkey Agar.