Listeria detection · Step 4 – confirmation
Tryptone Soya Yeast Extract Agar – purification and confirmation of Listeria
Tryptone Soya Yeast Extract Agar (TSYEA) is a non-selective nutrient agar used to purify suspect Listeria colonies before confirmation. Pure colonies from TSYEA are used for catalase, Gram stain, motility, haemolysis and biochemical tests.
- Purification of suspect Listeria colonies
- Listeria colonies appear bluish under oblique light
- Dehydrated powder, 500 g bottle · COLO code PRO7502
How Tryptone Soya Yeast Extract Agar works
Tryptone, soya peptone and yeast extract support good growth of Listeria without selective agents. Viewed with oblique transmitted light (Henry illumination), Listeria colonies show a typical bluish, granular appearance.
Technical data
| Preparation | 51 g per litre of water; boil to dissolve and sterilise at 121 °C for 15 min |
| Final pH | 7.2 ± 0.2 |
| Incubation | 30 ± 1 °C, 24–48 h |
| Storage | Dry, dark place; close the cap tightly after use |
| Shelf life | 3 years unopened |
Applications and practical notes
Tryptone Soya Yeast Extract Agar is used in the confirmation step of ISO 11290-1. Typical applications include:
- purification of suspect colonies from selective agars
- preparation of cultures for catalase, Gram and motility tests
- preparation of inocula for identification kits
- maintenance of Listeria reference cultures
Working with Tryptone Soya Yeast Extract Agar: Streak one typical colony from each selective plate for single colonies and incubate until colonies of 1–2 mm have developed. Use only pure cultures for the confirmation tests.
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.
Tryptone Soya Yeast Extract 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 Tryptone Soya Yeast Extract Agar, please send us a request. With every delivery of Tryptone Soya Yeast Extract Agar you receive the lot number and expiry date, and on request we send the available documentation for Tryptone Soya Yeast Extract Agar.
Where Tryptone Soya Yeast Extract 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 |
|---|---|---|
| Tryptone Soya Yeast Extract Agar | PRO7502 | 500 g |
| Tryptone Soya Yeast Extract Broth | PRO7506 | 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
COLO LabExperts
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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.
