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2nd June 2014  Content supplied by: IDEXX Laboratories Inc

Detect Pseudomonas aeruginosa in 24 hr from Healthcare Waters

A pan-european comparative study, has demonstrated that IDEXX's Pseudalert®/QuantiTray® test method for the 24-hour detection of Pseudomonas aeruginosa, is suitable for the analysis of waters encountered within a healthcare environment.

The need to monitor hospital water systems for the presence of P. aeruginosa has been emphasised in the UK in recent years and has resulted in revised guidance from the Department of Health. Appendix 4 of the HTM-04-01 Addendum (1) has been developed to provide technical guidance for a range of laboratories that have the capability and capacity to test for the presence of P. aeruginosa.

Within this appendix it is stated that ‘alternative water-testing methods other than [membrane] filtration that can show equivalence and/or improvement on the sensitivity and enumeration of P. aeruginosa are also acceptable’.

“The IDEXX Pseudalert method has undergone a rigorous and comprehensive Pan-European comparative study to demonstrate suitability for the analysis of waters encountered within a healthcare environment,” commented Andrew Headland, IDEXX Senior Business Manager for Europe, Middle East and North Africa. “The study, which involved seven laboratories, was designed and executed according to guidelines specified within ISO 17994:2004 which is the accepted method of the European Commission for the comparison of two water microbiology methods.”

The data generated were analysed by leading independent consultant, David Sartory, using the statistical procedures outlined in The Microbiology of Drinking Water (MoDW) (2) – Part 3 and according to ISO 17994:2004 (3).

The conclusion was that Pseudalert/Quanti-Tray is a more sensitive method for detecting P. aeruginosa from hospital water samples. Based on these outcomes it is concluded that Pseudalert/Quanti-Tray is a suitable, and potentially superior, alternative method to either the MoDW Part 8 method used extensively within the UK drinking water sector or the ISO 16266 method which is referenced within the HTM-04-01 guidelines for the analysis of P. aeruginosa.

The key coordinators of the study, which has been submitted for peer-reviewed publication, were Dr John Lee, Dr Susanne Lee, Prof. Philippe Hartemann and Prof. Martin Exner. These experts, who are world-renowned figures in the area of environmental microbiology and public health, have endorsed the findings and conclusions in support of the suitability of Pseudalert and Quanti-Tray for detecting P. aeruginosa in waters taken from the healthcare environment.

The Pseudalert test is based on a bacterial enzyme detection technology that signals the presence of P. aeruginosa through the hydrolysis of a substrate in the Pseudalert reagent. P. aeruginosa cells rapidly grow and reproduce using the rich supply of amino acids, vitamins and other nutrients present in the Pseudalert reagent. Actively growing strains of P. aeruginosa have an enzyme that cleaves the substrate in the reagent to produce blue fluorescence under ultraviolet light.

Pseudalert detects P. aeruginosa at 1 CFU in either 100 ml or 250 ml water samples and gives a confirmed result within 24 hours.


(1) UK Department of Health. Water Systems: Health Technical Memorandum 04-01: Addendum Pseudomonas aeruginosa – advice for augmented care units. https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/140105/Health_Technical_Memorandum_04-01_Addendum.pdf.

(2) Environment Agency (Standing Committee of Analysts). The Microbiology of Drinking Water (2002) – Part 3 – Practices and procedures for laboratories. Methods for the Examination of Waters and Associated Materials. Nottingham: Environment Agency.

(3) ISO 17994:2004 Water Quality – Criteria for establishing equivalence between microbiological methods. Geneva: International Organization for Standardization.

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Date Published: 2nd June 2014

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