Blog / Focus: Infection Control

New study demonstrates accuracy of Legionella detection test

By Kristin Majeska / Special to Healthcare Facilities Today
January 10, 2019

Legionnaires’ disease cases have gone up by 400% in the last 14 years and healthcare facilities are increasingly on the hook to reduce their patients’ risk from this potentially deadly but highly preventable form of pneumonia. Regular testing for Legionella pneumophila is the only way to be certain that a water management plan is working properly to prevent patient exposure.

What kind of Legionella testing method should a facility have as part of its water management plan? A recent study concludes that one testing method has superior accuracy. This next generation culture method, Legiolert®, developed by IDEXX, was significantly better at finding L. pneumophila. In fact, the older ISO 17731-2 method was 200% more likely (than Legiolert) to miss samples positive for the pathogen. The accuracy of the Legiolert test matters because of the high potential costs of missing L. pneumophila in a building’s water system.

The cost of missing the mark

Healthcare facilities can no longer ignore the risk of Legionnaires’ disease. CMS standards and The Joint Commission requirements make it clear that healthcare facility executives and managers are responsible for taking effective prevention measures, and for good reason, since 9 out of 10 cases are preventable. At the same time, the average case of Legionnaires’ disease costs a U.S. hospital $42,8551. The total cost of a healthcare facility-acquired case of Legionnaires’ disease, however, can be even higher when including negative news coverage, legal battles, and million-dollar fines. It is critical to reduce that disease risk by using the most accurate method to determine the levels of L. pneumophila in your building’s water system and respond with the right measures.

Comparing methods

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. Within the comparison study, six accredited laboratories, including hospitals, a water company, and commercial laboratories, compared Legiolert and the combined ISO 117311 – 1/2 method used in Germany for the enumeration of Legionella pneumophila. Over eight months in 2016 and 2017, 527potable water samples from naturally contaminated building (cold tap) water and related systems (hot tap water, shower, circulation systems) were analyzed.

The researchers found that the Legiolert method was significantly better at finding
L. pneumophila in 100 mL samples compared to the ISO 11731-2 method. Legiolert also recorded a significantly greater number of positive samples for the 100 mL sample test volume.  On a presence-absence basis, the study found that Legiolert was less likely to give false negative results and ISO 17731-2 was twice as likely to miss positive samples as Legiolert, including samples that were above the German action limit. Moreover, Legiolert detection of only
L. pneumophila was not statistically different than the ISO 11731-2 method detection of all species of Legionella, including L. pneumophila.   

This study also evaluated the practicality of the Legiolert method, finding that Legiolert demonstrated key advantages such as ease of use and labor savings. The overall conclusion of the study is that “Legiolert represents a significant improvement in determining levels of L. pneumophila from drinking water and related samples.”

Testing accuracy

To prevent a costly case of Legionnaires’ disease, healthcare facilities must ensure their water safety management plans are effectively controlling Legionella pneumophila. This study demonstrates that Legiolert opens the way for healthcare facilities to more accurately detect and respond to this pathogen on their premises.

 Kristin Majeska, Senior Manager, IDEXX Water

1.     Naumova EN, Lissb A, Jagaid JS, Behlaue I, Griffiths JK. Hospitalizations due to selected infections caused by opportunistic premise plumbing pathogens (OPPP) and reported drug resistance in the United States older adult population in 1991-2006. J of Public Health Policy. 2016;37(4)500-512. doi: 10.1057/s41271-016-0038-8
2.     Spies K, Pleischl S, Lange B, et al. Comparison of the 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. Int J Hyg Environ Health. 2018;221(7):1047–1053.

 

 

 

 

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