Media Perfringens agar 500gr, Oxoid CM0543

Description Oxoid Perfringens Agar (OPSP), is based on the formulation developed by Handford1. The medium utilises sulphadiazine (100µg/ml), oleandomycin phosphate (0.5µg/ml) and polymyxin B sulphate (10IU/ml), presented as freeze-dried supplements (SR0076 and SR0077) to give a high degree of selectivity and specificity for Clostridium perfringens. Sodium metabisulphite and ammonium ferric citrate are used as an indicator of sulphite reduction by Clostridium perfringens which produces black colonies on this medium when using a pour plate technique. Tests for confirmation of Clostridium perfringens are described in a study initiated by the International Commission on Microbiological Specifications for Foods (I.C.M.S.F.)2. Sulphite reducing bacteria other than Clostridium perfringens such as salmonellae, Proteus spp. and Citrobacter freundii, as well as staphylococci and Bacillus species, are inhibited on OPSP Agar. Perfringens Agar (OPSP), also, has the advantage of inhibiting growth of Clostridium bifermentans and Clostridium butyricum. These sulphite reducing organisms grow readily on Shahidi-Ferguson Perfringens Agar (SFP)3 and Tryptone-Sulphite-Neomycin Agar (TSN)4 as black colonies with a tendency to spread and obscure the whole surface of the medium. Occasional strains of enterococci will grow on Perfringens Agar (OPSP) as white colonies, easily distinguished from the large black colonies of Clostridium perfringens. Clostridium perfringens enumeration media which include egg yolk in order to detect lecithinase activity have not proved satisfactory partly because Clostridium perfringens colonies may frequently fail to produce haloes and thus appear falsely to be negative, and partly because counting is rendered impractical as the organism often grows in the form of large spreading colonies which completely blacken the medium5.