E. coli O157 · Selective enrichment
Modified Tryptone Soya Broth with Novobiocin – selective enrichment of E. coli O157
Modified Tryptone Soya Broth with Novobiocin (mTSB+n) is the selective enrichment broth for E. coli O157 in the horizontal method ISO 16654. Novobiocin and bile salts suppress much of the accompanying flora, so that O157 can grow to detectable numbers.
- Selective enrichment of E. coli O157 (ISO 16654)
- Novobiocin and bile salts improve selectivity
- Followed by IMS and plating on CT-SMAC
How Modified Tryptone Soya Broth with Novobiocin works
The tryptone-soya base with glucose and phosphate supports fast growth of E. coli. Novobiocin inhibits Gram-positive bacteria and some Gram-negative competitors such as Proteus, and bile salts add further selectivity. After enrichment at 41.5 °C, O157 cells are concentrated by immunomagnetic separation and plated on CT-SMAC and a second selective agar.
Typical reactions
| Organism | Reaction |
| E. coli O157:H7 | Turbid growth |
| Enterococcus faecalis | No growth |
Applications and practical notes
E. coli O157 and other Shiga toxin-producing E. coli (STEC) are tested in meat, raw milk products, sprouts and vegetables, for example according to ISO 16654 and FDA BAM Chapter 4a. Typical applications include:
- Raw and minced meat, especially beef
- Raw milk and raw-milk cheese
- Sprouts, leafy greens and other fresh produce
- Outbreak investigations and environmental samples
Working with Modified Tryptone Soya Broth with Novobiocin: Incubate the enrichment at 41.5 °C and carry out immunomagnetic separation after 6 hours and again after 18–24 hours, as described in ISO 16654.
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 coliform and E. coli methods: coliforms and E. coli are counted either by the multiple-tube (MPN) method, with a presumptive broth followed by confirmation broths, or by colony counts on selective agars. FDA BAM Chapter 4 describes both approaches for food and water, and ISO 16649-2 gives the colony-count method for β-glucuronidase-positive E. coli on TBX Agar. E. coli O157 and other STEC need dedicated media, serology and PCR. COLO.Science offers media, supplements, rapid tests, identification kits and QC strains for every step.
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.
Modified Tryptone Soya Broth with Novobiocin is supplied by COLO.Science in the pack sizes listed under Ordering information. For larger quantities, regular deliveries or method-specific sets that include Modified Tryptone Soya Broth with Novobiocin, please send us a request. With every delivery of Modified Tryptone Soya Broth with Novobiocin you receive the lot number and expiry date, and on request we send the available documentation for Modified Tryptone Soya Broth with Novobiocin.
Where Modified Tryptone Soya Broth with Novobiocin fits in E. coli O157 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 |
|---|---|---|
| Modified Tryptone Soya Broth with Novobiocin (mTSB+n) | PRO7559 | 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.
