Lauryl tryptose broth is a selective medium for the detection of coliforms in water and wastewater. This formulation is based on the Mallmann and Darby formulation. The tryptone provides the required carbon, nitrogen and vitamins in this medium. Lactose is a fermentable carbohydrate. The sodium chloride maintains the osmotic balance whilst the dipotassium hydrogen phosphate and potassium hydrogen phosphate act as buffers. Sodium lauryl sulphate is a selective again used to inhibit non-coliforms.