Iron Sulphite Agar is a medium for the detection of thermophilic anaerobic organisms causing sulphide spoilage in food, and is not intended for use in the diagnosis of disease or other conditions in humans.

This formulation is a modification of Cameron Sulphite Agar, which was developed by the National Canners Association of America (now the Grocery Manufacturers Association). Iron Sulphite Agar has a reduced concentration of sodium sulphite to allow improved detection of some strains of Clostridium sporogenes. Beerens, and later Mossel, demonstrated that some strains of C. sporogenes would not tolerate sodium sulphite levels of 0.1%. Mossel further observed that reducing sulphite content to 0.05% improved detection of these strains.

Tryptone provides nitrogen and other nutrients necessary to support bacterial growth. The presence of sulphite reducing bacteria is indicated by the formation of black colonies. These colonies form when bacteria reduce sulphite to sulphide, which reacts with iron (III) citrate to yield a black precipitate.

• Analyte: clostridium, desulfotomaculum, thermophilic, anaerobes
• Platform: dehydrated culture media
• Formula: tryptone 10.0g/L, sodium sulphite 0.5g/L, iron (III) citrate 0.5g/L, agar 12.0g/L
• Grams per litre: 23.00
• Litres per 500g: 22.00
• Plates per 500g: 1,190.00