Sulfite-reducing clostridia · Plate count
Iron Sulphite Agar – count of sulfite-reducing clostridia
Iron Sulphite Agar is a medium for the count of sulfite-reducing clostridia in food, feed and water. Under anaerobic conditions these bacteria form black colonies.
- Sulfite-reducing clostridia
- Black colonies under anaerobic incubation
- Food, feed and water
How Iron Sulphite Agar works
Sulfite and an iron salt act as an indicator: bacteria that reduce sulfite to sulfide form black iron sulfide in their colonies. Anaerobic incubation favours clostridia over aerobic bacteria.
Typical colony appearance
| Organism | Colonies |
| Clostridium perfringens | Black colonies |
Technical data
| Preparation | 42 g/L; boil to dissolve, dispense, autoclave 121 °C 15 min, cool to about 50 °C |
| Final pH | 7.6 ± 0.2 |
| Incubation | 35–37 °C, anaerobic, 24 h |
| Storage | Dry, dark place; keep the container tightly closed |
| Shelf life | 3 years unopened |
Applications and practical notes
Clostridium perfringens and other sulfite-reducing clostridia are indicators of hygiene and faecal contamination in food, feed and water, counted for example according to ISO 7937 and ISO 15213-1. Typical applications include:
- Meat, poultry and ready meals
- Spices, dried foods and animal feed
- Drinking water and recreational water
- Hygiene and process control
Working with Iron Sulphite Agar: Use pour plates or deep tubes and incubate anaerobically; count all black colonies as sulfite-reducing clostridia.
Good practice with dehydrated media: keep the bottle tightly closed in a cool, dry place, weigh the powder quickly to avoid moisture uptake, and use fresh distilled or deionised water. Check the pH of each new batch after preparation and before use, and label prepared media with the date. Performance of each lot can be verified with reference strains according to ISO 11133, the standard for the preparation, production, storage and performance testing of culture media.
About the Clostridium methods: Clostridium perfringens in food and feed is counted according to ISO 7937 on Tryptose Sulfite Cycloserine (TSC) Agar under anaerobic conditions, where sulfite reduction gives black colonies, and ISO 14189 describes the membrane filtration method for water. Sulfite-reducing clostridia are counted on iron sulfite agar according to ISO 15213-1. COLO.Science offers media, supplements, rapid tests and QC strains for these methods.
Complete sets from one supplier: COLO.Science supplies culture media, supplements, rapid tests, identification kits and QC strains as complete sets for the method you follow. Send us your sample types and standards, and we will prepare an offer with the matching products and documentation.
Iron Sulphite Agar is supplied by COLO.Science in the pack sizes listed under Ordering information. For larger quantities, regular deliveries or method-specific sets that include Iron Sulphite Agar, please send us a request. With every delivery of Iron Sulphite Agar you receive the lot number and expiry date, and on request we send the available documentation for Iron Sulphite Agar.
Where Iron Sulphite Agar fits in Clostridium testing
- Plate count – TSC Agar with D-cycloserine, anaerobic, 37 °C, 20 h
- Sulfite-reducing clostridia – Iron Sulphite Agar and supplements, anaerobic
- Confirmation – nitrate, lactose, gelatin and motility tests; PCR or LAMP
- Quality control – Clostridium sporogenes reference strains
See all Clostridium products in the Microbiology Catalogue →
Ordering information
| Product | COLO code | Pack |
|---|---|---|
| Iron Sulphite Agar | PRO7552 | 500 g |
Product notice: preparation, storage conditions and shelf life are given on the label. Technical data on this page are for orientation; the label and the lot documentation apply. B2B prices are quoted net, excluding VAT.
Sales and technical support
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Quotations and technical support for culture media and microbiology products across our international sales territory. B2B prices are net, excluding VAT.
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Need the complete set for your method?
Send the sample type, target organism and the standard you follow. COLO.Science will put together the media, supplements, QC strains and confirmation tests for the whole procedure.
