For detection of presumptive pathogenic Yersinia enterocolitica
SS AGAR (SALMONELLA SHIGELLA AGAR) is used for differential and selective isolation of Salmonella and Shigella species. This medium consists of Peptic digest of animal tissue and Meat extract which provides nitrogen, vitamins, minerals and amino acids essential for growth. Lactose is the fermentable carbohydrate providing carbon and energy. Bile salts and Sodium citrate inhibit Gram-positive bacteria, most coliform bacteria and swarming Proteus spp., while allowing Salmonella spp. to grow. Brilliant green and high concentrations of Sodium thiosulphate and citrate largely inhibit the accompanying microbial flora. Sodium Deoxycholate is an ionic detergent useful for disrupting and dissociating protein interactions. Sulphide production is detected by using thiosulphate and iron ions, the colonies turn black. The presence of coliform bacteria is established by detecting degradation of lactose to acid with the pH indicator neutral red. Neutral red is the pH indicator. Non-lactose fermenting bacteria (supposed pathogens) produce clear colonies, transparent or colorless, while coliforms are sufficiently inhibited, and form small colonies that vary from pink to red in color. The plates of the medium can be kept for at least a week in refrigeration. This formulation, highly selective, is not recommended for the primary isolation of Shigella. Some Shigella spp. may be inhibited.