Tryptose Sulphite Neomycin Agar is recommended for selective isolation and enumeration of Clostridium perfringens in food or other specimens. Tryptose and yeast extract provide nitrogenous compounds, vitamin B complex and other growth nutrients. Neomycin and polymyxin B sulphate inhibit gram-negative enteric bacilli. Neomycin is lethal for C. bifermentans. The colonies of C.perfringens are black due to the ferric sulphide formed after the sulphite reduction.