Listeria detection · selective isolation
Chromogenic L. monocytogenes Agar – chromogenic second plating medium
Chromogenic L. monocytogenes Agar is a selective chromogenic medium for the isolation and presumptive identification of Listeria monocytogenes. It is used as a second plating agar next to the Ottaviani-Agosti type medium and is completed with its selective supplement.
- L. monocytogenes: green to blue-green colonies
- Second chromogenic agar for Listeria
- Dehydrated powder, 500 g bottle · COLO code PRO7590
How Chromogenic L. monocytogenes Agar works
Chromogenic substrates make L. monocytogenes colonies green to blue-green, while selective agents in the supplement suppress most accompanying bacteria and fungi.
Typical colony appearance
| Organism | Colonies |
| L. monocytogenes | green to blue-green, smooth, small, regular |
Technical data
| Preparation | 47.3 g per litre of water; boil to dissolve, sterilise at 121 °C for 15 min, cool to about 50 °C and add the supplement (each vial dissolved in 1 mL sterile water) |
| Final pH | 7.1 ± 0.2 |
| Incubation | 35–37 °C, 24 ± 3 h |
| Storage | Powder 2–30 °C, dry and dark; prepared plates 2–8 °C, up to 1 week |
| Shelf life | 2 years |
Applications and practical notes
Chromogenic L. monocytogenes Agar is used as a second plating medium for Listeria, as allowed in ISO 11290-1. Typical applications include:
- ready-to-eat foods, cooked meat products and delicatessen
- milk, cheese and other dairy products
- fish, seafood and smoked fish
- environmental swabs from food production areas
Working with Chromogenic L. monocytogenes Agar: Streak a loopful of the enrichment culture so that well-isolated colonies develop, and incubate the plates inverted. Typical colonies are subcultured on TSYEA for confirmation.
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 L. monocytogenes 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 L. monocytogenes Agar, please send us a request. With every delivery of Chromogenic L. monocytogenes Agar you receive the lot number and expiry date, and on request we send the available documentation for Chromogenic L. monocytogenes Agar.
Where Chromogenic L. monocytogenes Agar fits in the Listeria workflow
- Primary enrichment – Half-Fraser Broth
- Secondary enrichment – Fraser Broth
- Selective isolation – chromogenic Listeria agar (Ottaviani-Agosti type) plus PALCAM or Oxford Agar
- Confirmation – subculture on TSYEA, biochemical identification and latex
Ordering information
| Product | COLO code | Pack |
|---|---|---|
| Chromogenic L. monocytogenes Agar | PRO7590 | 500 g |
| Chromogenic Listeria monocytogenes Agar Supplement | PRO7707 | 10 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.
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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.
