Endo Agar Base is a differential and moderately selective culture medium. It can be used for the detection and confirmation of coliforms and other enteric microorganisms in waters, milk, dairy and other food products. It uses fuchsin to differentiate between positive lactose-fermenting and lactose non-fermenting bacteria. Acetaldehyde production by lactose-fermenting organisms such as E. coli produce characteristic red colonies and a red surrounding area, marked by its reaction with Sodium sulphite in the presence of fuchsin. Lactose non-fermenters form colourless, transparent colonies. Peptone provides nitrogen, vitamins, minerals, and amino acids essential for growth. Lactose is the fermentable carbohydrate providing carbon and energy. Dipotassium phosphate acts as a buffer system and bacteriological agar is the solidifying agent.