Salmonella detection · Step 4 – confirmation
Urea Agar Base – urease test for the confirmation of Salmonella
Urea Agar Base is completed with sterile urea solution and used in slants for the urease test. Salmonella is urease negative, so the test helps to exclude Proteus and other urease-positive enterobacteria during confirmation.
- Salmonella: urease negative, medium stays yellow-orange
- Used in ISO and USA FDA methods
- Dehydrated powder, 500 g bottle · COLO code PRO7440
How Urea Agar works
Organisms that produce urease split urea into ammonia, which raises the pH and turns the phenol red indicator pink-red. Urease-negative organisms such as Salmonella do not change the colour of the medium.
Reading the reactions
| Reaction | Appearance |
| Urease positive | pink-red |
| Urease negative (Salmonella) | no colour change |
Technical data
| Preparation | 21 g per litre of water; boil to dissolve, sterilise at 121 °C for 15 min, cool to 50–55 °C and add sterile urea solution (e.g. 20 mL of 20 % urea per 200 mL); dispense as slants |
| Final pH | 7.2 ± 0.2 |
| Incubation | 36 ± 1 °C, 24 ± 2 h |
| Storage | Dry, dark place; close the cap tightly after use |
| Shelf life | 3 years unopened |
Applications and practical notes
Urea Agar is used for the urease test in the confirmation of Salmonella according to ISO 6579-1 and FDA BAM Chapter 5. Typical applications include:
- confirmation of suspect colonies from selective agars
- exclusion of urease-positive Proteus
- food and feed microbiology
- identification of enterobacteria
Working with Urea Agar Base: Add the sterile urea solution only to the cooled base, because urea is destroyed by heat. Streak the slant heavily and read after 24 h; a pink-red colour indicates a positive reaction.
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.
Urea Agar Base is supplied by COLO.Science in the pack sizes listed under Ordering information. For larger quantities, regular deliveries or method-specific sets that include Urea Agar Base, please send us a request. With every delivery of Urea Agar Base you receive the lot number and expiry date, and on request we send the available documentation for Urea Agar Base. If you are changing to Urea Agar Base from another supplier, we are happy to advise on the transition.
Where Urea 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 |
|---|---|---|
| Urea Agar Base, dehydrated | PRO7440 | 500 g |
| Triple Sugar Iron Agar, dehydrated | PRO7439 | 500 g |
| Lysine Iron Agar, dehydrated | PRO7522 | 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.
