Legionnaires’ disease is one of the most widely-known infections caused by waterborne bacterial contamination. The threat is particularly relevant in hospitals as the risk is particularly severe for immuno-compromised individuals, including oncology patients receiving chemotherapy, intensive care patients and those suffering from diabetes.
The cause of Legionnaires’ disease is the Legionella bacteria, which is found in natural fresh water environments. Legionella poses the greatest risk in engineered water systems; it is estimated that up to 70% of all building water systems have some degree of contamination. With their concentrated populations of high-risk individuals, hospitals and healthcare facilities are the greatest concern for public health. Non-potable sources include evaporative cooling systems, with which many major outbreaks have been associated, and potable water sources including taps, showers, ice machines, humidifiers and hydrotherapy pools.
For facilities managers, the threat of Legionella within a water system is magnified by its ability to form and thrive in biofilm, which can build up on any damp nonsterile surface, including the components of plumbing systems. As biofilm forms, microorganisms proliferate, and sections may break off as ‘planktonic’ waterborne components. These free-floating forms of Legionella have the potential to seed new biofilm colonies elsewhere in a water system or to emerge from the system in a potentially infectious aerosol.
There are approximately 60 species of Legionella, however Legionella pneumophila is the primary causative agent of Legionnaires’ disease. In 2016, there were 355 recorded confirmed cases of Legionnaires’ disease in England and Wales. 99.7% of these were caused by Legionella pneumophila,1 and hence, this species remains the main focus for Legionella risk mitigation.
Effective testing for Legionella pneumophila
To combat the dangers of Legionella, facilities managers should implement an effective water management plan, validated with regular testing. Establishing a dedicated water safety team and undertaking a risk assessment to identify the high-risk points where Legionella might grow are the first steps in this process. Each plan will be unique and tailored specifically to a facility, which may be more challenging in older hospital buildings, where water systems could have been adapted and altered many times during its use.
Every water management plan should be validated with effective and rapid testing for Legionella, to demonstrate that the plan is effectively mitigating the risk of Legionella. For years, the only method available for testing for Legionella was a traditional spread plate culture. This method has several drawbacks, including low sensitivity and a high rate of false negative results. To address these issues, the IDEXX Legiolert® test was introduced in 2016. Legiolert is a liquid culture method that has been shown to be highly sensitive for Legionella pneumophila, and delivers confirmed results up to seven days faster than traditional plate culture testing and confirmation methods.
Legiolert has been extensively compared to traditional spread plate methods. and there are currently 11 peer-reviewed comparison studies that have evaluated over 2,000 environmental samples taken from all over the world. Nineteen different laboratories across 7 countries were involved in these studies, including the Italian Istituto Superiore di Sanità, the U.S. Environmental Protection Agency, as well as public and private laboratories.
All of the peer-reviewed research showed Legiolert to be at least as sensitive as the standard plate culture methods, with 9 of the 11 studies showing it to be statistically more sensitive. All of the studies showed Legiolert to be highly specific for the detection of Legionella pneumophila.
This independent research is supported by a number of certification and regulatory bodies: for example, the method has been published by ASTM International as “ASTM D8429-21: Standard Test Method for Legionella pneumophila in Water Samples Using Legiolert”; is specified as a recommended method in the by the UK’s Standing Committee of Analysts’ “blue book” publication, “The determination of Legionella bacteria in waters and other environmental samples (2020) – Part 2 – Culture Methods for their detection and enumeration”; and Legiolert is also recognised with AFNOR certification for hot and cold sanitary water and cooling tower water (Reference No IDX 33/06 06/19).
For hospital facilities managers, having confidence in the results of microbiology testing is vital, but rapid, targeted testing can put them in control and ensure the safety of buildings’ water systems and prevent unnecessary closures of wards while protecting the patients within them.
For more information on the studies, click here, and to find out more about Legiolert and IDEXX Water, contact:
IDEXX Water UK, Units 1B and 1C, Newmarket Business Park, Studlands Park Avenue, Newmarket, Suffolk CB8 7ER
T: 01638 676800
References
1 – Public Health England: Legionnaires’ disease in residents of England and Wales: 2016 Official statistics. Accessible here.
