Desoxycholate Agar is a selective and differential medium for the isolation and differentiation of Gram-negative enteric bacilli. Leifson demonstrated improved recovery of intestinal pathogens from specimens containing normal intestinal flora. The Desoxycholate and Citrate salts inhibit the development of the Gram-positive organisms. The Peptone mixture 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. Sodium chloride supplies essential electrolytes for transport and osmotic balance. Neutral red is a pH indicator. Bacteriological agar is the solidifying agent.