Coliforms and E. coli · Presence-absence test in water
Presence-Absence Broth – coliform P-A test for drinking water
Presence-Absence Broth (P-A Broth) is used for the qualitative detection of coliforms in 100 mL samples of treated drinking water. Instead of a count, the result shows whether coliforms are present or absent.
- Qualitative test for 100 mL samples
- Lactose fermentation with acid
- For treated drinking water
How Presence-Absence Broth works
The triple-strength broth is mixed with the water sample. Coliforms ferment lactose and the indicator changes colour. Positive bottles are confirmed in BGLB for coliforms and in EC or EC-MUG Broth for E. coli.
Applications and practical notes
Membrane filtration and presence-absence media are used for coliforms and E. coli in drinking water, source water and bottled water. Typical applications include:
- Drinking water and source water monitoring
- Bottled water and ice testing
- Swimming pool and process water checks
- Laboratories working with membrane filtration
Working with Presence-Absence Broth: Add the medium to the sample bottle aseptically and mix gently so that it dissolves completely before incubation.
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.
Presence-Absence 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 Presence-Absence Broth, please send us a request. With every delivery of Presence-Absence Broth you receive the lot number and expiry date, and on request we send the available documentation for Presence-Absence Broth.
Where Presence-Absence 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 |
|---|---|---|
| Presence-Absence Broth | PRO7520 | 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.
