Bismuth Sulphite Agar for selective isolation of Salmonellae from faeces, urine, sewage and other materials.
Bismuth Sulphite Agar is used for the selective isolation of Salmonella spp. Salmonella constitute the most taxonomically complex group of bacteria among Enterobacteriaceae. Bismuth Sulphite Agar is a modification of Wilson and Blair formula. Also this medium favors use of larger inoculum as compared to other selective media, as it has unique inhibitory action towards gram-positive organisms and coliforms. Peptone and Beef extract serve as sources as carbon, nitrogen, vitamins and essential growth factors. Disodium phosphate acts as a buffereing agent. Dextrose is a fermentable carbohydrate source of the growth of microorganisms. Bismuth Sulphite Indicator and Brilliant Green are complementary, inhibiting to Gram-positive bacteria and coliforms, allowing Salmonella spp. to grow. Ferrous Sulphate is used for H2S production. When H2S is present, the iron incorporated in medium is precipitated, and positive cultures produce the characteristic brown to black color with metallic sheen. Bismuth Sulphite Agar is the solidifying agent