Salmonella detection · Step 3 – selective isolation
Chromogenic Salmonella Agar – colour-coded isolation of Salmonella
Chromogenic Salmonella Agar is a selective chromogenic medium for the isolation and presumptive identification of Salmonella from food, feed and environmental samples. Salmonella forms magenta colonies that are easy to distinguish from the blue-green colonies of coliforms, so it works well as the second plating agar next to XLD Agar.
- Salmonella: magenta (purple-red) colonies
- Clear colour contrast to coliforms and other enterobacteria
- Dehydrated powder, 500 g bottle · COLO code PRO7582
How Chromogenic Salmonella Agar works
Selective agents suppress Gram-positive bacteria and part of the Gram-negative accompanying flora. A chromogenic substrate is cleaved by an enzyme typical for Salmonella, which colours its colonies magenta, while a second substrate stains coliforms and other enterobacteria blue-green.
Typical colony appearance
| Organism | Colonies |
| Salmonella | magenta (purple-red) |
| Coliforms | blue-green |
Suspect colonies are confirmed biochemically and serologically.
Technical data
| Preparation | 47.5 g per litre of water; heat to boiling to dissolve, do not autoclave; cool to about 50 °C and pour plates |
| Final pH | 7.0 ± 0.2 |
| Incubation | 35–37 °C, 24 h |
| Storage | Powder 2–30 °C, dry and dark; prepared plates 2–8 °C, up to 1 week |
| Shelf life | 2 years unopened |
Applications and practical notes
Chromogenic Salmonella Agar is used as a second plating medium next to XLD Agar, as recommended in ISO 6579-1. 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 Chromogenic Salmonella Agar: Streak a loopful of each enrichment culture on XLD Agar and on Chromogenic Salmonella Agar. The clear colour differentiation reduces the number of false-positive colonies that need to be confirmed. Prepared plates should be kept refrigerated and protected from light.
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.
Chromogenic Salmonella 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 Chromogenic Salmonella Agar, please send us a request.
Where Chromogenic Salmonella 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 |
|---|---|---|
| Chromogenic Salmonella Agar, dehydrated | PRO7582 | 500 g |
| XLD Agar, dehydrated | PRO7437 | 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.
