Pharmacopoeial media · Pharmaceutical water
R2A Agar – count of bacteria in purified water
R2A Agar is a low-nutrient agar for the count of heterotrophic bacteria in purified water, water for injection and drinking water. It recovers stressed and slow-growing bacteria that do not grow well on rich media.
- Low-nutrient agar for water testing
- Recovers stressed, slow-growing bacteria
- For membrane filtration and pour plates
How R2A Agar works
Low concentrations of peptones, yeast extract, glucose and starch, together with sodium pyruvate, favour bacteria adapted to nutrient-poor water. Longer incubation at a lower temperature gives higher counts than rich media.
Typical colony appearance
| Organism | Colonies |
| Pseudomonas aeruginosa | Greyish-white colonies |
| Bacillus subtilis | Greyish-white colonies |
Technical data
| Preparation | 18.1 g/L; boil to dissolve, autoclave 121 °C 15 min |
| Final pH | 7.2 ± 0.2 |
| Incubation | 30–35 °C (water testing: at least 5 days) |
| Storage | Dry, dark place; keep the container tightly closed |
| Shelf life | 3 years unopened |
Applications and practical notes
Purified water and water for pharmaceutical use contain stressed, slow-growing bacteria that are counted on low-nutrient media with long incubation, as described in the European Pharmacopoeia monograph for purified water and in USP <1231>. Typical applications include:
- Purified water and water for injection systems
- Monitoring of pharmaceutical water loops
- Low-nutrient and stressed bacteria
- Drinking and process water
Working with R2A Agar: Filter a suitable volume of water through a membrane, place it on the agar and incubate for at least 5 days before counting.
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 pharmacopoeial microbiological testing: the European Pharmacopoeia and the USP describe harmonised methods for non-sterile products – microbial enumeration (Ph. Eur. 2.6.12, USP <61>) and tests for specified micro-organisms (Ph. Eur. 2.6.13, USP <62>) – and the sterility test for sterile products (Ph. Eur. 2.6.1, USP <71>). The chapters define the media, incubation conditions and the growth promotion test that each batch of medium must pass with reference strains. COLO.Science offers the media, diluents, neutralisers and QC strains for these tests from one source.
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.
R2A 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 R2A Agar, please send us a request. With every delivery of R2A Agar you receive the lot number and expiry date, and on request we send the available documentation for R2A Agar.
Where R2A Agar fits in pharmaceutical water testing
- Sample preparation – Buffered Sodium Chloride-Peptone Solution, Tryptic Soy Broth and neutralising diluents
- Microbial enumeration – Tryptic Soy Agar (TAMC) and Sabouraud Dextrose Agar (TYMC)
- Specified micro-organisms – enrichment in Tryptic Soy Broth, then MacConkey, Mannitol Salt, Cetrimide, XLD, VRBG, RCM and Columbia media
- Sterility test – Fluid Thioglycollate Medium and Tryptic Soy Broth, 14 days
See all pharmacopoeial media in the Microbiology Catalogue →
Ordering information
| Product | COLO code | Pack |
|---|---|---|
| R2A Agar | PRO7480 | 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.
