Coliforms and E. coli · Chromogenic coliform count
Chromogenic Coliform Agar – coliforms in 24 hours
Chromogenic Coliform Agar is a plating medium for the detection and count of coliforms. A chromogenic substrate for β-galactosidase colours coliform colonies, so they can be read directly after 24 hours.
- Coliforms: coloured colonies
- Read after 24 hours
- No autoclaving – boil to dissolve
How Chromogenic Coliform Agar works
Coliforms have β-galactosidase, which splits the chromogenic substrate and releases a coloured product that stays in the colony. Selective agents suppress Gram-positive flora. No further confirmation tests are needed for the coliform count.
Typical colony appearance
| Organism | Colonies |
| Coliforms | Blue-green colonies |
Technical data
| Preparation | 32.8 g/L; heat to boiling until dissolved, cool to ~50 °C, pour plates (no autoclaving stated) |
| Final pH | 7.0 ± 0.2 |
| Incubation | 35-37 °C, 24 h |
| Storage | Powder 2-30 °C, dark, dry, sealed; prepared plates 2-8 °C up to 1 week |
| Shelf life | 2 years (sealed powder) |
Applications and practical notes
Plate count and isolation media for coliforms and E. coli are used in food, feed, water and hygiene testing, for example according to ISO 4832 and ISO 16649-2. Typical applications include:
- Coliform and E. coli colony counts in food and feed
- Isolation of lactose-fermenting Gram-negative bacteria
- Process hygiene criteria in dairy, meat and vegetable production
- Teaching and routine quality-control laboratories
Working with Chromogenic Coliform Agar: Store prepared plates at 2–8 °C, protected from light, and use them within one week.
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.
Chromogenic Coliform 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 Chromogenic Coliform Agar, please send us a request. With every delivery of Chromogenic Coliform Agar you receive the lot number and expiry date, and on request we send the available documentation for Chromogenic Coliform Agar.
Where Chromogenic Coliform Agar fits in coliform and E. coli testing
- Presumptive test – Lauryl Sulfate Tryptose Broth (MPN) or VRBL / chromogenic agar (colony count)
- Confirmation – BGLB Broth for coliforms; EC or EC-MUG Broth at 44.5 °C for E. coli
- Isolation – EMB, MacConkey, TBX or chromogenic E. coli agar
- Identification – IMViC kit; for O157 and STEC: SMAC or chromogenic O157 agar, latex and PCR
Ordering information
| Product | COLO code | Pack |
|---|---|---|
| Chromogenic Coliform Agar | PRO7579 | 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.
