Salmonella Chromogenic Agar 1122 Condalab

Salmonella Chromogenic Agar is a selective chromogenic medium. It can be used for the detection and presumptive identification of Salmonella species from clinical samples, foods, and waters. This type of media has been traditionally used to differentiate species of Salmonella from the rest of the Enterobacteriaceae family, (based on their capacity to produce hydrogen sulphide and their inability to ferment lactose). However, they are not adequate as there are more than 2,000 species of Salmonella which do not have these characteristics. Casein peptone and beef extract provide nitrogen, vitamins, minerals, and amino acids essential for growth. Chromogenic mixture, in conjunction with sodium citrate, aids in inhibiting Gram-positive organisms, Proteus and coliforms. Bacteriological agar is the solidifying agent in this medium. The addition of the supplement inhibits accompanying flora, avoiding possible false positive results.

To identify Salmonella species, this chromogenic agent is based on the combination of two chromogenic substrates that ease quick identification. Magenta colonies are a result of the hydrolysis of one of the chromogenic substrates by the Salmonella species due to the inability to utilise another chromogenic substrate. Microorganisms producing the enzyme that cleaves the second chromogenic substrate will produce blue-green colonies. Thus, non-Salmonella organisms appear blue-green or are not stained by any of the chromogens of the medium. Supplement is added when more selectivity is desired. The supplement inhibits the accompanying flora, specially Pseudomonas, that could appear in the same colour as Salmonella colonies. The medium can be used as a second medium for the detection of Salmonella in food and water according to ISO 6579 and ISO 19250 respectively.