Enterobacteriaceae · Differentiation
MR-VP Medium – methyl red and Voges-Proskauer tests
MR-VP Medium is a buffered glucose broth for the methyl red (MR) and Voges-Proskauer (VP) tests, used to differentiate Enterobacteriaceae, for example E. coli from Enterobacter in the IMViC series.
- Methyl red and VP tests in one broth
- Part of the IMViC series
- Use with MR and VP reagents
How MR-VP Medium works
Organisms with mixed-acid fermentation, such as E. coli, lower the pH so far that methyl red turns red. Organisms with butanediol fermentation, such as Enterobacter, produce acetoin, which gives a red colour with the VP reagents.
Typical results
| Organism | Reaction |
| Escherichia coli | MR positive (red), VP negative |
| Enterobacter aerogenes | MR negative, VP positive (red) |
Technical data
| Preparation | 17 g/L; heat with stirring to boiling, dispense, autoclave 121 °C 15 min |
| Final pH | 7.0 ± 0.2 |
| Storage | Cool, dry place away from bright light; keep the container tightly closed |
| Shelf life | 3 years |
Applications and practical notes
Enterobacteriaceae and coliforms are differentiated with classic biochemical tests such as the IMViC series (indole, methyl red, Voges-Proskauer, citrate). Typical applications include:
- Differentiation of coliforms and Enterobacteriaceae
- Water and food isolates
- Teaching and reference laboratories
- Confirmation of typical colonies
Working with MR-VP Medium: Divide the culture into two tubes after incubation and test one with Methyl Red Reagent and the other with VP Reagent A and B.
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 Enterobacteriaceae methods: Enterobacteriaceae are hygiene indicators in food and feed. ISO 21528-2 counts them on Violet Red Bile Glucose Agar, and ISO 21528-1 detects them after enrichment in Enterobacteria Enrichment Broth Mossel. Typical colonies are confirmed as oxidase-negative and glucose-fermenting. The European Pharmacopoeia and USP use the same broth and agar for bile-tolerant Gram-negative bacteria in non-sterile products. Kligler Iron Agar, Simmons Citrate Agar and identification kits are used to differentiate isolates. COLO.Science offers media, identification kits and QC strains for these steps.
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.
MR-VP Medium is supplied by COLO.Science in the pack sizes listed under Ordering information. For larger quantities, regular deliveries or method-specific sets that include MR-VP Medium, please send us a request. With every delivery of MR-VP Medium you receive the lot number and expiry date, and on request we send the available documentation for MR-VP Medium.
Where MR-VP Medium fits in Enterobacteriaceae testing
- Enrichment – Enterobacteria Enrichment Broth Mossel
- Enumeration and isolation – Violet Red Bile Glucose Agar
- Confirmation – oxidase test and glucose fermentation; Kligler Iron Agar, TSI and Simmons Citrate Agar for differentiation
- Identification – Enterobacteriaceae biochemical identification kit
See all Enterobacteriaceae products in the Microbiology Catalogue →
Ordering information
| Product | COLO code | Pack |
|---|---|---|
| MR-VP Medium | PRO8182 | 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.
