Ingredients : gms/lit.Heart infusion solids 10.00Proteose peptone 10.00Lactose 10.00Sodium citrate 20.00Ferric ammonium citrate 2.00Sodium deoxycholate 5.00Neutral red 0.02Agar 13.50Final pH (at 25°C) : 7.5 + 0.2Instrution for use : Suspend 70.52 grams in 1000 ml of distilled water. Heat to boiling to dissolve the medium completely. DONOT AUTOCLAVE. Avoid excessive heating as it is detrimental to the medium. Cool to 45-50°C. Mix welland pour into sterile petri plates.Principle :Heart infusion solids is a source of carbon and nitrogen. Deoxycholate Citrate Agar contains ProteosePeptone as a source of carbon, nitrogen, vitamins and minerals. Lactose is a carbohydrate. Sodium citrateand Sodium deoxycholate inhibit gram positive bacteria, coliforms and Proteus species. Ferric AmmoniumCitrate aids in the detection of H2S producing bacteria. Neutral Red is a pH indicator. Agar is a solidifyingagent.In the presence of neutral red, bacteria that ferment lactose produce acid and form red colonies. Bacteriathat do not ferment lactose form colorless colonies. If the bacteria produce H2S, the colonies will haveblack centers. The majority of normal intestinal bacteria ferment lactose and do not produce H2S (pink-redcolonies without black centers). Salmonella and Shigella sp. Do not ferment lactose but Salmonella mayproduce H2S (colourless colonies with or without black centers). Lactose – fermenting colonies may have azone of precipitation around them caused by the precipitation of deoxycholate in the presence of acid.