Abstract
To examine the impact of environmental factors on Legionella in drinking water distribution systems, the growth and survival of Legionella under various conditions was studied. When incubated in tap water at 4 °C, 25 °C, and 32 °C, L. pneumophila survival trends varied amongst the temperatures, with the stable populations maintained for months at 25 °C and 32 °C demonstrating that survival is possible at these temperatures for extended periods in oligotrophic conditions. After inoculating coupons of PVC, copper, brass, and cast iron, L. pneumophila colonized biofilms formed on each within days to a similar extent, with the exception of cast iron, which contained 1-log less Legionella after 90 days. L. pneumophila spiked in a model drinking water distribution system colonized the system within days. Chlorination of the system had a greater effect on biofilm-associated Legionella concentrations, with populations returning to pre-chlorination levels within six weeks. Biofilms sampled from drinking water meters collected from two areas within central Arizona were analyzed via PCR for the presence of Legionella. Occurrence in only one area indicates that environmental differences in water distribution systems may have an impact on the survival of Legionella. These results document the impact of different environmental conditions on the survival of Legionella in water.
Highlights
The Legionella genus contains over 50 species of gammaproteobacteria [1], many of which are capable of producing respiratory illness in humans
While a large number of studies have been aimed at investigating the incidence and survival of Legionella at the in-premise level, a relatively small amount of research has been focused on Legionella within main distribution systems [12], leading to a knowledge gap about their interactions with these systems
At 4 °C, after the first week of a steady state, Legionella concentration decreased at an exponential rate for two months before stabilizing at 102 colony forming units (CFU)/mL for the remainder of the study period
Summary
The Legionella genus contains over 50 species of gammaproteobacteria [1], many of which are capable of producing respiratory illness in humans. These bacteria are ubiquitous in both natural and artificial water systems, where their growth is often associated with biofilms. Legionella are capable of infecting a wide variety of eukaryotes, with humans being a potential incidental host. Able to survive in a wide range of temperatures, Legionella typically require relatively warm environments—often found in anthropogenic water systems—to reach population levels capable of posing public health risks to humans [5]
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