Salmonella Shigella Agar

Salmonella Shigella Agar is used for isolating Salmonella spp. and some strains of Shigella spp. The medium is widely used in sanitary bacteriology to isolate these species from feces, urine, and fresh canned foods. The presence of Bile Salts No. 3 and Brilliant Green suppresses the growth of Gram-positive bacteria, most coliforms, and Proteus spp. The high Lactose content allows for the early detection of slow Lactose-fermenting microorganisms, while both Thiosulphate and Ferric Acid help identify H2S-producing bacteria. While Lactose-fermenting microorganisms produce red or pink colonies on a reddish background due to the color shift of the pH indicator Netural Red, Shigella forms transparent colonies. H2S-producing bacteria like Salmonella can be distinguished by the formation of colonies with black center due to the production of iron sulfide.