Description
Tryptose Sulphite Cycloserine agar is formulated according to the method of Harmon et al1, using the basal medium developed by Shahidi and Ferguson2, but replacing the selective agents, Kanamycin Sulphate and Polymixin B, with D – Cycloserine to a level of 400mgm/litre. TSC agar conforms with Australian Standard Methods for Food Microbiology2. In a comparative study, Harmon et al were able to demonstrate that their TSC agar was more selective than SFP agar, inhibiting the growth of enterococci and the majority of coliforms, but that the yield of vegetative cells and spores of Clostridium perfringens was slightly lower3.
The sulphite reducing properties of Clostridium perfringens and some other members of the Genus Clostridia produce black colonies in the presence of Sodium metabisulphite and Ferric ammonium citrate, as the sulphite is reduced to sulphide and combines with the iron salt to form black ferric sulphide. Black colonies of Clostridium perfringens are usually surrounded by a halo caused by their lecithinase activity on the egg yolk in the medium. However, not all strains of Clostridium perfringens are lecithinase positive, and confirmatory testing of all black colonies on TSC agar should be performed. It should also be noted that lecithinase positive strains of some facultative anaerobes growing on TSC agar may interfere with the recognition of lecithinase positive strains of Clostridium perfringens. Omission of egg yolk from the medium, as proposed by Hauschild and Hilsheimer4, while removing a nutrient and an identification marker, may be advantageous in that the smaller colonies resulting allow for easier enumeration in the presence of large numbers of Clostridium perfringens in the sample.
Supplied in box of 10 x 100gm vials.
