A-1 Medium is used for the detection of fecal coliforms in drinking water, treated wastewater, seawater, and beverages. Enzymatic Digest of Casein provides nitrogenous sources and vitamins. Lactose and Salicin are the carbohydrate sources providing energy for bacterial growth. Sodium Chloride maintains the osmotic balance. Triton X-100 is a surfactant improving nutrient uptake by the bacteria.