Selective and differential medium for recovery of Salmonella and Shigella from clinical, water and dairy products. Deoxycholate Citrate Agar is a modification of Leifson formula and is recommended for the isolation of Salmonella and Shigella sp. Gram positive bacteria and coliforms are inhibited by the addition of sodium desoxycholate and sodium citrate to the formula. H2S producing microorganisms reduce ferric ammonium citrate to iron sulfide and give colonies with black centers. Fermentation of lactose by coliforms causes the pH to shift to acid with the neutral red dye color changing to red and bile to precipitate. Lactose fermenters form pink colonies with bile precipitated around the colonies. Lactose non-fermenters form colorless colonies.