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A new Australian has used a novel method in combination with standard detection methods to examine the effect of temporary water stagnation on Legionella and microbial communities present in a hospital water system.

A major challenge for Legionella management within large hospital systems is that under unfavourable conditions, Legionella transforms into a state (called viable but non culturable 鈥� VBNC) that cannot be detected using standard methods.

To understand the extent of the problem, Flinders University researchers conducted the first comprehensive study that quantified all Legionella, including those in the VBNC state, and free-living amoebae from a hospital water system under dynamic flow and temperature conditions.

鈥淲e took a different approach because we didn鈥檛 know how often the standard method was returning false negative results for Legionella and it鈥檚 really hard to determine the optimal management approach if you can鈥檛 trust your testing method,鈥� said Flinders University鈥檚 Associate Professor Harriet Whiley.

Using a commercially available monitoring system developed by Enware Australia, the researchers measured water temperature, number and duration of water flow events for a sample of hand basins and showers. Their analysis demonstrated that 21.8% of samples were positive for Legionella spp., 21% for L. pneumophila, 40.9% for V. vermiformis and 4.2% for Acanthamoeba.

Temporary water stagnation arising through intermittent usage (being less than 2 hours per month) significantly increased the amount of Legionella.

鈥淭emporary stagnation arising through intermittent usage causes water quality to deteriorate 鈥� and this study identified that temporary stagnation for over a month promotes the persistence of Legionella,鈥� Whiley said.

鈥淪imilarly, free-living amoeba and heterotrophic bacteria present in this temporary stagnant environment were positively correlated with Legionella. All samples positive for Legionella were also positive for amoeba.

鈥淭herefore, temporary stagnation and free-living amoeba must be managed for the proper control and prevention of Legionnaires鈥� disease.鈥�

The study also found that the standard microbiological culture method used to detect Legionella returned a false negative result for 88% of the Legionella positive samples 鈥� highlighting a need for future research to investigate concentrations of Legionella that pose a risk to public health, in order to inform improved Legionella guidelines.

The research 鈥� 鈥樷�� 鈥� has been published by Frontiers in Cellular and Infection Microbiology (Bacteria and Host section).

Image credit: iStock.com/Svitlana Hulko