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

SCA agar is a selective medium for the enumeration of sulfite-reducing clostridia in samples where the vegetative cells are predominant and which are therefore not subjected to heat shock (e.g. a pasteurisation step) before analysis. Selectivity is provided by D-cycloserine and sodium azide. The medium contains an indicator system involving sulfite and iron. Most unwanted species are suppressed, while Clostridium perfringens and related species will reduce the sulfite and form black colonies due to the production of ferrous sulfide (Eisgruber and Reuter, 1991, 1995). Originally the medium was prepared with higher amounts of D-cycloserine, sulfite and iron for the selective enumeration of Clostridium perfringens (Hauschild and Hilsheimer, 1974). Modifications and the addition of sodium azide as a further selective component were first recommended by Eisgruber (1986). A proposal for a standardised medium was delivered by Eisgruber and Reuter (1995).