The threat of Legionella within a water system comes from its ability to form and thrive in biofilm. Without free flowing of water within a system, biofilms build up as bacteria bind together to form a stable ‘community’, and can develop on any damp nonsterile surface, including all surfaces in drinking water distribution networks and domestic plumbing systems. As biofilm forms, the microorganisms proliferate, with sections able to break off and further seed new biofilm colonies elsewhere in a water system or to emerge from the system in a potentially infectious aerosol.

Recommendations for safe re-occupancy To protect public health, it is crucial for building owners and managers to safeguard their water systems from Legionella. In the U.S. and Europe, about one in 10 people who contract Legionnaires’ disease will die from it, according to the Centers for Disease Control and Prevention and the European Society of Clinical Microbiology and Infectious Diseases (ESCMID).

The ESCMID recently issued guidance for managing Legionella in building water systems during the COVID-19 pandemic. They identify several risk factors for Legionella growth, including: water temperatures between 25°C and 50°C; poor system flow; certain plumbing materials and aerosol formation.

“Water age, lack of movement, and lack of residual disinfection can

create an opportunity for waterborne microorganisms to flourish.”

When restarting a system that’s been closed or had the hot water shut off for more than one month, the ESCMID recommends monitoring temperatures and biocide levels, if applicable, for at least 48 hours before taking Legionella samples from the sentinel outlets. Microbiological

samples taken too soon after disinfection could give false- negative results.

In the Unites States, the Environmental Science, Policy & Research Institute (ESPRI) also offers recommendations on preparing buildings for re-occupancy. In buildings with at-risk populations, such as the elderly, the institute suggests sending water samples to a qualified laboratory for analysis. Flushing the entire building will help mitigate problems that emerged when water was stagnant, the guidance says. After flushing, additional water samples should be collected to determine whether these efforts were successful or should continue.

The COVID-19 pandemic has created unprecedented public health challenges around the globe. Building managers and owners need to be aware of the risks of Legionnaires’ disease and ensure the dangers of contamination within stagnant water can be minimised by accurate testing, so that buildings can be reopened safely.

Fast, accurate detection of

Legionella pneumophila In 2016, IDEXX introduced the Legiolert test, a new method that uses a liquid culture. The test is significantly faster than the spread-plate culture method, providing a confirmed result for Legionella pneumophila in seven days. Peer-reviewed studies also show Legiolert to be more accurate, more sensitive and, have shown the incidence of false negative results to be lower, so harmful bacteria are less likely to be missed. Legiolert was designed to identify all the serogroups of Legionella pneumophila, not just the most common serogroup.

The Legiolert liquid culture method removes the need for many of the laborious steps involved in the plate culture method and much of the associated variability. The agar plate is replaced by a liquid culture medium, which is much closer to the bacterium’s natural water habitat. Typically, the Legiolert reagent is added to a sample of water and includes the nutrients for the bacteria to grow, plus additives to suppress the growth of non-Legionella pneumophila bacteria. The reagent also contains an indicator which enables the target bacteria to be easily identified after incubation by a colour change, reducing the subjectivity of results.

Legiolert samples take between two and four minutes to prepare before they are added to an IDEXX Quanti- Tray, where the liquid is distributed between six large and 90 small reservoirs, sealed and incubated for seven days. The Legiolert colour indicator used for enumeration is extremely specific for the target Legionella pneumophila bacteria, thus there is no requirement for further confirmatory testing. The result is a testing protocol that is substantially faster. TOMORROW’S FM | 47

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