For isolation of Shigella species from food samples. It is recommended by BIS committee under specification IS:5887 (Part VII) 1999, reaffirmed 2005. Deoxycholate Citrate Agar Medium (as per BIS) is a moderately selective and differential plating medium used for isolating enteric bacilli, particularly Salmonella and many Shigella species. Sodium deoxycholate is inhibitory to gram positive bacteria. Most intestinal flora gets inhibited due to citrate in the medium. Coliforms produce pink colored colonies whereas non lactose fermenters appear as colorless colonies. The organisms known to reduce ferric ammonium citrate to iron sulphide are indicated by blackening of the central position of colony. Meat extract and protease peptone serves as a source of carbon and nitrogen. Lactose is the fermentable carbohydrate and neutral red as pH indicator helping in differentiation of enteric bacilli as lactose ferments produce red colonies while non lactose produce colorless colonies. Gram positive bacteria, coliforms and proteus species is inhibited due to sodium citrate and sodium deoxycholate. Ferric ammonium citrate aids in the detection of H2S producing bacteria. If the bacteria produce H2S, the colonies will have black centers. The majority of normal intestinal bacteria ferment lactose and do not produce H2S (red colonies without black centers). Salmonella and Shigella spp. do not ferment lactose but Salmonella may produce H2S (Colorless colonies with or without black centers).Lactose fermenting colonies may have a zone of precipitation around them caused by the precipitation of deoxycholate in the presence of acid.