Coliforms and E. coli · Presumptive MPN test · granulated
Lauryl Sulfate Tryptose Broth – granulated format for dust-free weighing
The granulated Lauryl Sulfate Tryptose Broth has the same use as the powder: it is the presumptive broth of the multiple-tube method for coliforms and E. coli. Granules produce less dust, flow better and dissolve evenly.
- Granules – less dust when weighing
- Presumptive broth for coliform MPN counts
- Gas in Durham tube = presumptive positive
How Lauryl Sulfate Tryptose Broth works
Lactose fermentation with gas production, under selective pressure from sodium lauryl sulfate, separates coliforms from most of the accompanying flora. Positive tubes are confirmed in Brilliant Green Lactose Bile Broth for coliforms or in EC Broth at 44.5 °C for E. coli.
Typical reactions
| Organism | Reaction |
| Coliforms | Turbidity and gas filling at least 1/3 of the Durham tube |
| Enterococcus faecalis | No gas |
Technical data
| Preparation | 35.6 g/L; boil with stirring until dissolved; dispense into tubes with Durham tubes; autoclave 121°C 15 min |
| Final pH | 6.8±0.2 |
| Incubation | 35-37°C for 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 Sulfate Tryptose Broth: Weigh the granules without grinding them, dissolve completely before dispensing and keep the bottle closed between uses.
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 Sulfate Tryptose Broth 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 Sulfate Tryptose Broth, please send us a request. With every delivery of Lauryl Sulfate Tryptose Broth you receive the lot number and expiry date, and on request we send the available documentation for Lauryl Sulfate Tryptose Broth.
Where Lauryl Sulfate Tryptose Broth 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 Sulfate Tryptose Broth (LST), granulated | PRO7615 | 250 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.
