IDEXX have announced the publication of a peer reviewed Pan European study*, in The Journal of Water and Health "Evaluation of an MPN test for the rapid enumeration of Pseudomonas aeruginosa in hospital waters (doi:10.2166/wh.2014.187 - in press).”

The paper concludes that the IDEXX Pseudalert®/Quanti-Tray® method,  for the rapid detection of Pseudomonas aeruginosa (P. aeruginosa), produces confirmed results in a shorter time than the standard reference ISO 16266 and MoDW Part 8 PACN agar membrane filtration methods with no further confirmation steps. The authors also concluded that Pseudalert/Quanti-tray was a valid alternative method for hospital water analysis.

The study, conducted on both routine hospital water samples (80 from six laboratories) and artificially contaminated samples (192 from five laboratories), compared in parallel the performance of the traditional membrane filtration technique, which produces presumptive positive results in a 40-48 hour timeframe, with the Pseudalert/Quanti-Tray test, which gives confirmed results after 24 hours. For routine samples, the data indicated at least equivalent performance of Pseudalert/Quanti-Tray, while for the artificially contaminated samples, the data revealed higher counts of P. aeruginosa being recorded by Pseudalert/Quanti-Tray.

The report also concluded that as the Pseudalert/Quanti-Tray method does not require confirmation testing for atypical strains of P.aeruginosa, it can save up to six days of additional analysis and has the added advantage of providing confirmed counts within 24 hours incubation, compared to 40–48 hours or longer for the ISO 16266 and MoDW Part 8 methods.

All comparison studies were conducted in accordance with ISO 17994:2014.

“This study clearly demonstrates that the Pseudalert/Quanti-Tray method is an acceptable alternative to the ISO 16266:2006 and MoDW Part 8 PACN agar methods for the enumeration of P. aeruginosa from hospital waters and has the additional benefit of giving a more rapid confirmed result,” commented David Sartory, independent consultant, authority on water microbiology, and one of the paper’s authors. He added “This is particularly important during the investigation of possible hospital acquired infections, enabling appropriate action to be taken to protect patients within as short a timescale as possible, while also enabling the more rapid identification of uncontaminated outlets so that they can be safely returned to use within 24 hours.”

Launched in 2011, the IDEXX 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, which  recently won the prestigious ‘Product Innovation in Healthcare’ Award at the Institute of Healthcare Engineering and Estate Management’s (IHEEM) Annual Exhibition, detects P. aeruginosa at 1 CFU in standard 100 ml water samples and gives a confirmed result within 24 hours.

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 24 hours after which the fluorescent cells can be counted and quantified by reference to an MPN table.

* The full text can be accessed at www.iwaponline.com/jwh/up/wh2014187.htm  “Evaluation of an MPN test for the rapid enumeration of Pseudomonas aeruginosa in hospital waters” David P. Sartory, Danièle Pauly, Nathalie Garrec, Lucia Bonadonna, Maurizio Semproni, Christiane Schell, Annika Reimann, Susan J. Firth, Christopher Thom, Philippe Hartemann, Martin Exner, Henning Baldauf, Susanne Lee and John V. Lee.