Listeria detection · selective isolation
Oxford Agar – selective agar for Listeria
Oxford Agar is a selective and differential plating medium for Listeria monocytogenes and other Listeria species in food and environmental samples. It is used as a second plating agar and is completed with Oxford Agar Supplement.
- Listeria: grey-green colonies with black sunken centre and black halo
- Second plating agar for Listeria
- Dehydrated powder, 500 g bottle · COLO code PRO7471
How Oxford Agar works
Lithium chloride and the antibiotics in the Oxford supplement suppress most Gram-negative and many Gram-positive bacteria and fungi. Listeria hydrolyses aesculin, and the reaction with ferric ions forms a black zone around the colonies.
Typical colony appearance
| Organism | Colonies |
| Listeria | grey-green, with black sunken centre and black halo |
Technical data
| Preparation | 56.5 g per litre of water; boil to dissolve, sterilise at 121 °C for 15 min, cool to about 50 °C and add Oxford supplement (A + B) per 100 mL |
| Final pH | 7.0 ± 0.2 |
| Incubation | 35–37 °C, 24 h |
| Storage | Dry, dark place; close the cap tightly after use |
| Shelf life | 3 years unopened |
Applications and practical notes
Oxford Agar is used as a second plating medium for Listeria in food and environmental testing, for example with FDA BAM Chapter 10. 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 Oxford 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 Listeria culture method: the reference method for Listeria monocytogenes in the food chain, ISO 11290-1, uses primary enrichment in Half-Fraser Broth, secondary enrichment in Fraser Broth, plating on a chromogenic agar of the Ottaviani-Agosti type and a second selective agar, and confirmation of typical colonies. The FDA BAM Chapter 10 uses Buffered Listeria Enrichment Broth instead. COLO.Science offers media, supplements, rapid tests, identification kits and QC strains for every step.
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.
Oxford 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 Oxford Agar, please send us a request. With every delivery of Oxford Agar you receive the lot number and expiry date, and on request we send the available documentation for Oxford Agar.
Where Oxford 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 |
|---|---|---|
| Oxford Agar Base, dehydrated | PRO7471 | 500 g |
| Oxford Agar Supplement | PRO7708 | 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.
