Endo Agar was originally designed for the isolation of Salmonella typhi but is now preferred for lactose-fermenting and non-fermenting intestinal organisms, particularly coliforms. Peptone supplies nitrogenous compounds and vitamins, being Lactose the fermentable carbohydrate. The combination of Sodium Sulfite and Basic Fuchsin suppresses the growth of many Gram-positive microorganisms. Lactose-fermenting coliforms produce pink-red colonies with a characteristic green sheen, while those bacteria unable to ferment this sugar form pale pink or colorless colonies. Agar is the gelifying agent.