Coliforms and E. coli · MPN with fluorescence
Lauryl Tryptose Broth with MUG – coliforms and E. coli in one tube
Lauryl Tryptose Broth with MUG combines the presumptive coliform test with a fluorogenic test for E. coli. MUG (4-methylumbelliferyl-β-D-glucuronide) is split by β-glucuronidase, and positive tubes show blue fluorescence under UV light at 366 nm.
- Gas = coliforms; fluorescence = E. coli
- MUG read under long-wave UV (366 nm)
- Saves a separate E. coli confirmation step
How Lauryl Tryptose Broth with MUG works
About 95 % of E. coli strains produce β-glucuronidase. The enzyme releases 4-methylumbelliferone from MUG, which fluoresces blue under UV light. Gas in the Durham tube indicates coliforms. Note that E. coli O157:H7 is normally β-glucuronidase negative, so it does not fluoresce.
Typical reactions
| Organism | Reaction |
| E. coli (GUD-positive) | Blue-white fluorescence at 366 nm |
| E. coli O157:H7 | No fluorescence |
| Coliforms | Gas in Durham tube |
Technical data
| Preparation | 35.7 g/L; boil to dissolve, autoclave 121 °C 15 min |
| Final pH | 6.8 ± 0.2 |
| Incubation | 36 ± 1 °C, 18-24 h |
| Storage | Dry, dark place; keep the container tightly closed |
| Shelf life | 3 years unopened |
Applications and practical notes
In the multiple-tube (MPN) method for coliforms and E. coli, as described in FDA BAM Chapter 4 and ISO 4831, a presumptive broth is followed by confirmation broths. Typical applications include:
- Coliform and E. coli MPN counts in food and feed
- Testing of water, ice and beverages
- Hygiene monitoring in dairy, meat and ready-to-eat production
- Verification of media and methods with reference strains
Working with Lauryl Tryptose Broth with MUG: Use glassware that does not fluoresce, include a positive and a negative control tube and read fluorescence in a darkened room.
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.
Lauryl Tryptose Broth with MUG is supplied by COLO.Science in the pack sizes listed under Ordering information. For larger quantities, regular deliveries or method-specific sets that include Lauryl Tryptose Broth with MUG, please send us a request. With every delivery of Lauryl Tryptose Broth with MUG you receive the lot number and expiry date, and on request we send the available documentation for Lauryl Tryptose Broth with MUG.
Where Lauryl Tryptose Broth with MUG 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 |
|---|---|---|
| Lauryl Tryptose Broth with MUG (LST-MUG) | PRO7543 | 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
COLO LabExperts
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.
COLO.SCIENCE | MICROBIOLOGY SUPPORT
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.
