IDEXX has shared the results of a new potable water study carried out by independent water microbiology experts. The study, “Comparison of Legiolert®/Quanti-Tray® MPN test for the enumeration of Legionella pneumophila from potable water samples with the German regulatory requirements methods ISO 11731-2 and ISO 11731,” was recently published in the International Journal of Hygiene and Environmental Health. The study concludes that, “The new method (Quanti-Tray/Legiolert) represents a significant improvement in the enumeration of L. pneumophila from drinking water and related samples.”

L. pneumophila causes 97% of Legionnaires’ disease cases according to data from cultures of 4,719 patients over seven years in 17 countries.*

Within the comparison study, six accredited laboratories, including hospitals, a water company, and commercial laboratories compared Legiolert and the German combined ISO 117311 - 1 / 2 approach for the enumeration of Legionella pneumophila, over the period of August 2016 to March 2017.

The study found the IDEXX Legiolert method to be significantly more sensitive for the recovery of L. pneumophila for 100mL samples compared to the ISO 11731-2 method, and states that Legiolert could be an acceptable and potentially superior alternative to the combined current German ISO 11731-2/ISO 11731 testing procedure.

Legiolert also recorded a significantly greater number of positive samples for the 100 mL sample test volume, and additionally provided counts of L. pneumophila that were not statistically different than the ISO 11731-2 method provided for all species of Legionella.

On a presence-absence basis, the study found that the ISO 17731-2 method was twice as likely to miss positive samples as Legiolert, including samples that were above the German action limit. The study also evaluated the practicality of the Legiolert method, finding that it demonstrated advantages such as ease of use and labour-saving.

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*European Centers for Disease Control data