Salmonella Differential Agar, Modified, 2.5 kg

Salmonella Differential Agar is slight modification of original formulation of Rambach (1) used for differentiation of Salmonella species from Proteus species and other enteric bacteria. Production of acid from propylene glycol is a novel characteristic of Salmonella species and is utilized in these media. Many of the media such as SS Agar, XLD Agar recommended for the identification and differentiation of Salmonella species (2) are based on lactose fermentation and hydrogen sulphide production. Peptone special and yeast extract supports the luxuriant growth of bacteria while sodium deoxycholate inhibits gram-positive organisms rendering the medium selective for enteric microorganisms. The BC indicator turns pink in presence of acid produced from propylene glycol. Lactose fermenting ability is determined by using an indicator, which can detect the presence of enzyme ß-galactosidase. Lactose fermenting (ß-galactosidase producing) bacteria yield blue violet colored colony (3). Salmonellae produce acid from propylene glycol and on combining with the pH indicator gives typical pink red colonies. Other enteric gram-negative bacteria form colourless colonies. Salmonella Typhimurium and Salmonella Enteritidis produce pink to red colonies. Specimen should be enriched in an appropriate selective enrichment broth. This enriched culture is then inoculated on Salmonella Differential Agar, Modified and incubated at 35-37°C for 24-48 hours. Storage and Shelf-life: Store dehydrated powder in tightly closed container and prepared medium at 2-8°C. Use before expiry period on the label. References: 1. Rambach A., 1990, Appl Environ. Microbiol., 56:301. 2. Eaton A.D., Clesceri L.S., Rice E. W. and Greenberg A W., (Eds.), 2005, Standard Methods for the Examination of Water and Wastewater, 21st Ed., APHA, Washington, D.C. 3. Greenwald R., Henderson R.W. and Yappaw S., 1991, J. Clin. Microbiol. 29:2354.