The IDEXX Colilert-18/Quanti-Tray (ISO 9308-2:2012) total coliform/E.coli test, for the 18 hour detection of E.coli and total coliforms in water, has been specified as a reference method, under EN ISO 9308-2, in the European Drinking Water Directive 2015/1787.

The amendment of the annexes II and III of the Council Directive 98/83/EC on the quality of water intended for human consumption has now been published in the European Official Journal, after being adopted by the European Commission on October 6^th, 2015, and came into force on October 27^th, 2015. The text has to be transposed into national legislation within a period of 24 months by the EC Member States, by October 27^th, 2017 at the latest.

The Colilert-18 test became the ISO 9308-2 standard for the detection of E.coli and total coliforms in water in 2012, and later as EN ISO 9308-2 in 2014, following extensive validation, and provides quantified results in as little as 18 hours with no further confirmation of results required. It is also U.S. EPA-approved and approved and included in Standard Methods for Examination of Water and Wastewater. 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.” The full text of the Commission Directive 2015/1787 can be found in the Official Journal of the European Union in 23 different languages.

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 minimal amounts of training and equipment are required 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.