CAMFIL HVAC Filtration Solutions

Study Confirms Accuracy of Legionella Test Method

16.03.2021, 21:53

Study Confirms Accuracy of Legionella Test Method

An independent study supports claims from IDEXX about the efficacy of its Legiolert solution for detecting Legionella pneumophila in non-potable water.

Undertaken in the Netherlands by leading organisation in the field of water quality and water technology, WLN, the study compared Legiolert with Dutch national reference method, NEN 6265, which is comparable to ISO 11731 in the detection of Legionella pneumophila.

Comparing both potable and non-potable water samples, the study concluded that the “Legiolert method performed as well as the standard NEN 6265 method in detection of Legionella pneumophila in potable and non-potable water samples. In non-potable water Legiolert is a better method for detection of Legionella pneumophila than culturing on solid media due to disturbing overgrowth of other bacteria on those plates, which is not a factor of concern with Legiolert.”

According to data from cultures of 4,719 patients over seven years in 17 countries,1 Legionella. pneumophila causes 97 per cent of Legionnaires’ disease cases. Non-potable sources of Legionella pneumophila include evaporative cooling systems, and data from the Centers for Disease Control (CDC) show that in the U.S., Legionella pneumophila has been the only cause of cooling tower related disease outbreaks.2

The latest findings support the conclusions of other trials conducted with Legiolert. In 2019, the testing solution  received NF Validation by AFNOR certification, which involved a rigorous multi-step process that judged Legiolert to be equivalent to standards ISO 11731 and to NF T90-431, the culture method used in France, with trial results from 14 laboratories demonstrating strong reproducibility of the Legiolert method. Peer-reviewed studies also show it to be more accurate and more sensitive, and, importantly, these have shown the incidence of false negative results is lower, so dangerous bacteria are less likely to be missed.3 Legiolert was designed to identify all the serogroups of Legionella pneumophila, not just the most common, serogroup 1.

In 2020, Legiolert was accepted by the UK’s Standing Committee of Analysts (SCA) and is specified as a recommended method in the Committee’s “blue book” publication of “The determination of Legionella bacteria in waters and other environmental samples (2020) – Part 2 – Culture Methods for their detection and enumeration.

Legiolert uses bacterial enzyme detection technology to identify and enumerate Legionella. pneumophila in drinking water and other building water systems. It supplies nutrients which allow any target Legionella pneumophila cells present in a water sample to grow rapidly, and an indicator in the reagent changes colour to signal their presence. The test reagent also contains inhibitors to supress non-target organisms to avoid overgrowth of other bacteria.

The test is simple to use and requires minimal training and equipment to set up, giving confirmed results in 7 days, around half the time of traditional agar-based methods. Legiolert simplifies and accelerates water testing, reducing risks posed by the potentially fatal Legionnaires’ disease by generating highly reliable data and enabling faster remedial action.


1    European Centre for Disease Prevention and Control data

2   US Centers for Disease Control & Prevention (CDC) Vital Signs, June 2017

3   Spies, K. Pleischl, B., Lange B., Longer, B., Hübner, J., Jurzki, L., Luden, K., Exner, M. International Journal of Hygiene and Environmental Health 221 (2018) 1047–1053. Full text at

CAMFIL HVAC Filtration Solutions

Staff Reporter covers the latest news, trends and opinion from the facilities management (FM) and corporate real estate (CRE) sectors. The FM market is currently estimated to be worth USD 1 trillion annually and is projected to grow at a compounded annualised rate of approximately 5% between now and 2026.

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