Coliforms and E. coli · Selective enrichment
MacConkey Broth Purple – lactose broth with purple indicator
MacConkey Broth Purple is a MacConkey-type broth with bromocresol purple as the pH indicator. Lactose fermenters turn the broth yellow. It is used for the enrichment and presumptive detection of coliforms and E. coli.
- Purple broth turns yellow with acid
- Bile salts for selectivity
- For coliform enrichment and presumptive tests
How MacConkey Broth Purple works
Lactose fermentation produces acid, and bromocresol purple changes from purple to yellow. Bile salts inhibit Gram-positive bacteria. Positive broths are subcultured on selective agar for isolation.
Typical reactions
| Organism | Reaction |
| E. coli | Turbid growth, yellow |
| Staphylococcus aureus | No growth |
Technical data
| Preparation | 35 g/L; boil to dissolve, dispense, autoclave 121°C 15 min |
| Final pH | 7.3 ± 0.2 |
| Incubation | 42-44°C, 24 h (growth) / 48 h (selectivity) |
| Storage | Dry, dark place; keep the container tightly closed |
| Shelf life | 3 years |
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 MacConkey Broth Purple: Compare each tube with an uninoculated control, because the colour change can be gradual.
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.
MacConkey Broth Purple is supplied by COLO.Science in the pack sizes listed under Ordering information. For larger quantities, regular deliveries or method-specific sets that include MacConkey Broth Purple, please send us a request. With every delivery of MacConkey Broth Purple you receive the lot number and expiry date, and on request we send the available documentation for MacConkey Broth Purple.
Where MacConkey Broth Purple 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 |
|---|---|---|
| MacConkey Broth Purple | PRO7514 | 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.
