Salmonella detection · Step 2 – selective enrichment
Fluid Tetrathionate Medium – selective enrichment broth for Salmonella
Fluid Tetrathionate Medium is a selective enrichment broth for Salmonella in food and in the microbial examination of non-sterile pharmaceutical products. The base is completed with iodine–iodide solution before use and is used together with a second enrichment broth.
- Selective enrichment step of the Salmonella method
- Used in USA FDA and USP methods
- Dehydrated powder, 500 g bottle · COLO code PRO7483
How Fluid Tetrathionate Medium works
Iodine added before use reacts with sodium thiosulfate to form tetrathionate. Salmonella can reduce tetrathionate and grow, while most coliforms are inhibited. Bile salts suppress Gram-positive bacteria and calcium carbonate neutralises the acid formed during incubation.
Applications and practical notes
Fluid Tetrathionate Medium is used for the selective enrichment of Salmonella in the FDA BAM Chapter 5 procedures and in pharmacopoeial testing. Typical applications include:
- raw meat, poultry and highly contaminated foods
- feed and animal by-products
- non-sterile pharmaceutical products
- environmental samples
Working with Fluid Tetrathionate Medium: Complete the base with iodine–iodide solution just before use and do not heat the complete broth again. It is used together with a second enrichment broth of a different principle, such as RV Broth.
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.
Fluid Tetrathionate Medium is supplied by COLO.Science in the pack sizes listed under Ordering information. For larger quantities, regular deliveries or method-specific sets that include Fluid Tetrathionate Medium, please send us a request.
Where Fluid Tetrathionate Medium fits in the Salmonella workflow
- Pre-enrichment – Buffered Peptone Water or Lactose Broth
- Selective enrichment – RV Broth and tetrathionate 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 |
|---|---|---|
| Fluid Tetrathionate Medium, dehydrated | PRO7483 | 500 g |
| Fluid Tetrathionate Broth Supplement | PRO7669 | 2 × 5 vials |
| Tetrathionate / MKTTn Broth Supplement | PRO7668 | 2 × 5 vials |
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.
