Enterobacteriaceae · Differentiation
Koser Citrate Medium – citrate utilisation in liquid medium
Koser Citrate Medium is a liquid medium for the citrate utilisation test, used to differentiate E. coli (citrate negative) from Enterobacter and other citrate-positive bacteria, for example in the IMViC series.
- Citrate as the only carbon source
- Liquid medium – turbidity = positive
- Part of the IMViC series
How Koser Citrate Medium works
Sodium citrate is the only carbon source and ammonium phosphate the only nitrogen source. Organisms that can use citrate grow and make the broth turbid; organisms that cannot use citrate leave it clear.
Typical results
| Organism | Result |
| Citrate positive (e.g. Enterobacter) | Turbid broth |
| Escherichia coli | No growth, clear broth |
Technical data
| Final pH | 6.7 ± 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 Koser Citrate Medium: Inoculate lightly with a straight needle from a single colony, so that no nutrients are carried over.
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.
Koser Citrate 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 Koser Citrate Medium, please send us a request. With every delivery of Koser Citrate Medium you receive the lot number and expiry date, and on request we send the available documentation for Koser Citrate Medium.
Where Koser Citrate 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 |
|---|---|---|
| Koser Citrate Medium | PRO8183 | 100 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.
