Desoxycholate Citrate Agar is a moderately selective and differential plating medium used for isolating enteric bacilli, particularly Salmonella and many Shigella species.

• Infusion from meat is a source of carbon and nitrogen
• Peptone provides carbon, nitrogen, vitamins, and minerals
• Lactose is the fermentable carbohydrate
• Sodium citrate and sodium desocycholate inhibit gram-positive bacteria
• Ferric ammonium citrate aids in the detection of H2S-producing bacteria
• Neutral red is a pH indicator
• Agar is the solidifying agent

In the presence of neutral red, bacteria that ferment lactose produce acid and form red colonies. Bacteria that do not ferment lactose form colorless colonies. If the bacteria produce H2S, the colonies will have black centers.