Salmonella detection · Step 3 – selective isolation
Bismuth Sulfite Agar – highly selective agar for Salmonella, including S. Typhi
Bismuth Sulfite (BS) Agar is a highly selective plating medium for the isolation of Salmonella, including S. Typhi, from food and other samples with a heavy accompanying flora. It is used in the USA FDA Salmonella method together with XLD and Hektoen Enteric Agar.
- Salmonella: black to grey-green colonies, often with metallic sheen
- Used in USA FDA methods
- Dehydrated powder, 500 g bottle · COLO code PRO7467
How Bismuth Sulfite Agar works
Bismuth sulfite and brilliant green inhibit Gram-positive bacteria and most coliforms. Salmonella reduces sulfite to sulfide, which reacts with iron salts and forms black colonies, often with a metallic sheen and a black or brown zone around them.
Typical colony appearance
| Organism | Colonies |
| Salmonella | black to grey-green, possibly with metallic sheen |
Plates should be prepared shortly before use and read after 40–48 h, as some strains develop slowly.
Technical data
| Preparation | 47.3 g per litre of water; heat to boiling to dissolve, avoid overheating, do not autoclave; cool to 48 ± 2 °C and pour plates; use within 48 h |
| Final pH | 7.5 ± 0.2 |
| Incubation | 35–37 °C, 40–48 h |
| Storage | Dry, dark place; close the cap tightly after use |
| Shelf life | 3 years unopened |
Applications and practical notes
Bismuth Sulfite Agar is a plating medium in the FDA BAM Chapter 5 procedures, recommended especially for S. Typhi and lactose-positive strains. Typical applications include:
- meat, poultry, eggs and egg products
- milk, dairy products and infant formula
- feed, spices and dry foods
- environmental swabs from the food production area
Working with Bismuth Sulfite Agar: Prepare the plates shortly before use and do not autoclave the medium. Typical colonies may need 40–48 h to develop, so plates are read again after the second day before they are reported negative.
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 Salmonella culture method: the reference method for Salmonella in the food chain, ISO 6579-1, has four steps: non-selective pre-enrichment, selective enrichment in two broths, plating on two selective agars and confirmation of typical colonies. The FDA BAM Chapter 5 follows the same principle with media adapted to different food types. Rapid tests and identification kits shorten the time to result, but positive screening results are usually confirmed by the culture method. COLO.Science offers products for every step, so that one supplier covers the whole procedure.
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.
Bismuth Sulfite 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 Bismuth Sulfite Agar, please send us a request.
Where Bismuth Sulfite Agar fits in the Salmonella workflow
- Pre-enrichment – Buffered Peptone Water or Lactose Broth
- Selective enrichment – RVS Broth and MKTTn Broth
- Selective isolation – XLD Agar plus a second selective or chromogenic agar
- Confirmation – TSI, Lysine Iron Agar, Urea Agar, latex and biochemical identification
See the complete Salmonella set in the Microbiology Catalogue →
Ordering information
| Product | COLO code | Pack |
|---|---|---|
| Bismuth Sulfite Agar, dehydrated | PRO7467 | 500 g |
| XLD Agar, dehydrated | PRO7437 | 500 g |
| Hektoen Enteric Agar, dehydrated | PRO7441 | 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.
