IDEXX's Colilert®-18 test, for 18-hour detection of E. coli and total coliforms in water, has been approved as a reference method, through the transposition of the European Drinking Water Directive 2015/1787 into national legislation in 25 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.

The 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 (Colilert-18) provides all necessary specifications for performing the enumeration of E. coli and total coliform bacteria.”

“Colilert is used by water utility companies around the world to ensure the safety of drinking water for millions of consumers, and the regulatory assurance the test has, by being an ISO reference method, is testament to its efficiency, reliability and performance,” commented Philippe Rousselin, EMEA Regulatory Manager for IDEXX Water. “The inclusion of Colilert-18 into the European Drinking Water Directive has now widened its potential reach into additional markets.”

With its high sensitivity, specificity and rapid results, giving accurate and fast indications of any potential faecal contamination, Colilert-18 is simple to use and requires only minimal amounts of training and equipment to allow operatives to set up and interpret the results in just 18 hours.

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. This step takes less than 1 minute of hands-on time. 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.