DCLS Agar is a selective medium for the primary isolation of Salmonella and Shigella from fecal specimens and urine. The gram positive organisms, coliforms and Proteus are completely or partially inhibited by sodium citrate, sodium thiosulfate and sodium desoxycholate. Proteose peptone and beef extract provides nitrogen, vitamins, minerals and amino acids essential for growth. Lactose and sucrose are the fermentable carbohydrates, providing carbon and energy. Neutral red is the pH indicator. Bacteriological agar is the solidifying agent. It can be used with direct streaking or with an enrichment for Salmonella in Sodium Selenite Broth (Cat. 1222) or Selenite Cystine Broth (Cat.1220). It is preferable to inoculate in duplicate: one heavily and the other diluted. The presence of two carbohydrates in the formulation assures the formation of red colonies of those organisms, which ferment one or both of the carbohydrates. The majority of Shigella organisms yield colorless colonies, but some strains of S. flexneri, as well as other species of Shigella, grow rapidly giving colonies that are a weak pink but are distinguished easily from Proteus or the coliforms. If Salmonella or Shigella are suspected, the colonies should be subcultured on other media for identification, such as Kligler Iron Agar (Cat. 1042), Nitrate Motility Medium Base (Cat. 1565) or Triple Sugar Iron Agar (Cat. 1046).
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