This monograph has been assessed by members of the IUMS–ICFMH Working Party on Culture Media and given ‘Approved’ status.

The medium utilises the selective inhibitory properties of D-cycloserine and an indicator system involving sulfite and ferric iron. Most unwanted organisms are suppressed, while Clostridium perfringens and related species will reduce the sulfite and form black colonies due to the production of ferrous sulfide. Originally the medium was used with the addition of egg yolk (Harmon et al., 1971), but the egg yolk-free modification is more convenient (Hauschild and Hilsheimer, 1974a, 1974b) and this has been adopted for the detection of the organism in water (Sartory, 1986). A membrane filtration technique (Burman et al., 1969) was incorporated into water testing in 1982. The selectivity of the medium for Clostridium perfringens can be increased by raising the incubation temperature to 44°C. The medium without D-cycloserine is also known as iron sulfite agar (q.v.) and used for the enumeration of mesophilic sulfite-reducing clostridia.