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Colilert®-18 Approved as Water Microbiological Reference Method for the Rapid Identification of Bacterial Contamination in Drinking Water

ISO Standard Method is included in European Drinking Water Directive, now Transposed into National Legislation

IDEXX, a global leader in rapid microbiological testing for water, has announced that the Colilert®-18 test, for 18-hour detection of E. coli and total coliforms in water, had been approved as a reference method, through the transposition of the European Drinking Water Directive 2015/1787 into the national legislation of member countries.

The Directive, which came into force on October 27th, 2015 gave European countries 24 months to transpose the legislation into national law. All 28 member countries of the EU have now either approved Colilert-18 as a reference method, through the transposition of the European Drinking Water Directive 2015/1787 into national legislation, or approved Colilert-18 as an alternative method before the revision of the European Drinking Water Directive.

Idexx web summer 2018The Colilert-18 test, which became the ISO 9308-2 standard for the detection of E. coli and total coliforms in water in 2012, and EN ISO 9308-2 in 2014, following extensive validation, provides quantified results in as little as 18 hours with no further confirmation of results required. Colilert-18 is also U.S. EPA-approved, included in 'Standard Methods for Examination of Water and Wastewater' and in the UK's Microbiology of Drinking Water 'Blue Book'. The amendment to the European Drinking Water Directive now states that "EN ISO 9308-2:2014 (Colilert-18) provides all necessary specifications for performing the enumeration of E. coli and total coliform bacteria."

Colilert-18 is a wide-reaching testing platform for drinking water, sewage discharge, raw water and bio-solids, with numerous independent tests placing it at the forefront of contamination detection and confirming its ability to enhance long term performance across networks.

It is a fast, easy-to-use solution which delivers confirmed results in the 18-hour timeframe and no other test offers these levels of speed and flexibility. The process itself also saves time in the laboratory, as it takes less than one minute of hands-on time per sample and detects coliforms and E. coli simultaneously.

Colilert is a global solution manufactured by IDEXX Laboratories and one which is now protecting two billion people worldwide from coliforms such as E. coli, having been approved in more than 40 Countries. Colilert®-18 spots contamination early, meaning remediation work can be carried out quickly before coliforms spread and create unnecessary time and cost consequences.

The product consists of a reagent powder, which is added to a standard 100ml water sample and then incubated for 18 hours in the case of presence/absence determination. The presence of E. coli and total coliforms is subsequently determined following incubation, with coliforms indicated by the sample turning yellow, and fluorescence indicating the presence of E. coli. Where quantification of a sample is required, IDEXX has developed a simple device known as a Quanti-Tray®, which consists of 51 individually sealable cells. The Quanti-Tray can also be incubated for 18 hours, after which the fluorescent cells can be counted and quantified.

For more information contact IDEXX Water on +44 (0) 1638 676 800 or visit or email This email address is being protected from spambots. You need JavaScript enabled to view it.