TSN Agar (Tryptone Sulfite Neomycin) is a selective medium that can be used in tubes or plates for the identification and enumeration of Clostridium perfringens in foods and other materials, especially from mixed contaminating flora. The Casein peptone provides nitrogen, vitamins, minerals and amino acids essential for growth. Yeast extract is source of vitamins, particularly the B-group. Ferric citrate and Sodium sulfite are H2S indicators. C. perfringens reduces the sulfite to sulfide which reacts with the iron and forms a black iron sulfide precipitate, seen as black colonies. Bacteriological agar is the solidifying agent. Polymyxin and Neomycin sulfates inhibit the growth of the majority of Enterobacteria and Clostridium bifermentans. The incubation at a temperature of 46°C allows specific and quantitative results.
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