Pharmacopoeial media · Enterobacteriaceae
Violet Red Bile Glucose Agar – count of Enterobacteriaceae
Violet Red Bile Glucose Agar (VRBG) is a selective agar for the detection and count of Enterobacteriaceae. It is used in food testing according to ISO 21528 and in the pharmacopoeial test for bile-tolerant Gram-negative bacteria.
- Count of Enterobacteriaceae
- Food (ISO 21528) and pharmaceutical testing
- No autoclaving needed
How Violet Red Bile Glucose Agar works
Bile salts and crystal violet suppress Gram-positive flora. Glucose fermenters acidify the medium, and neutral red colours their colonies red to purple, often with a halo of precipitated bile.
Typical colony appearance
| Organism | Colonies |
| Escherichia coli | Red colonies, often with purple-red halo |
| Salmonella Typhimurium | Red colonies |
| Staphylococcus aureus | Inhibited |
Technical data
| Preparation | 38.5 g/L; heat to boiling until dissolved; do not autoclave |
| Final pH | 7.4 ± 0.2 |
| Incubation | 30–37 °C, 18–24 h (according to the method) |
| Storage | Dry, dark place; keep the container tightly closed |
| Shelf life | 3 years unopened |
Applications and practical notes
Tests for specified micro-organisms in non-sterile products, described in Ph. Eur. 2.6.13 and USP <62>, combine an enrichment in soya-bean casein digest broth with selective media for each organism and confirmation of typical colonies. Typical applications include:
- Raw materials and active ingredients
- Oral and topical non-sterile products
- Herbal products and food supplements
- Method suitability and growth promotion tests
Working with Violet Red Bile Glucose Agar: Pour plates with an overlay of the same medium to keep colonies small and typical, and read them after 18–24 hours.
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.
Violet Red Bile Glucose 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 Violet Red Bile Glucose Agar, please send us a request. With every delivery of Violet Red Bile Glucose Agar you receive the lot number and expiry date, and on request we send the available documentation for Violet Red Bile Glucose Agar.
Where Violet Red Bile Glucose Agar fits in pharmacopoeial 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 |
|---|---|---|
| Violet Red Bile Glucose Agar (VRBG) | PRO7432 | 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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Polje ob Sotli 4, SI-3255, Slovenia
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.
