This is a base medium to which can be added selective supplements of choice for the presumptive identification and enumeration of Clostridium perfringens in food products using poured plate techniques. Sodium metabisulphite and Ferric ammonium citrate are included in the base and together provide an indicator of sulphite reaction by Clostridium perfringens, which produces black colonies on the medium.  It is recommended that this medium be used with an overlay otherwise cultures may not grow as black colonies. NB: This is a base medium only and contains no selective supplements.