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Impact of environmental factors on legionella populations in drinking water.

Schwake DO, Alum A, Abbaszadegan M - Pathogens (2015)

Bottom Line: Chlorination of the system had a greater effect on biofilm-associated Legionella concentrations, with populations returning to pre-chlorination levels within six weeks.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.

View Article: PubMed Central - PubMed

Affiliation: School of Life Sciences, Arizona State University, Tempe, AZ 85281, USA. david.schwake@asu.edu.

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.

No MeSH data available.


L. pneumophila concentrations in biofilms on coupons submerged in tap water incubated at 25 °C. Error bars indicate standard error between duplicate samples of each culture.
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pathogens-04-00269-f002: L. pneumophila concentrations in biofilms on coupons submerged in tap water incubated at 25 °C. Error bars indicate standard error between duplicate samples of each culture.

Mentions: For all pipe materials, similar Legionella biofilm association (105 to 2.7 × 105 CFU/cm2) was observed three days after inoculation (Figure 2). After the initial three days, concentrations in biofilms formed on cast iron decreased before stabilizing at 1.2 × 103 CFU/cm2 for the duration of the study, resulting in a 2-log reduction. Concentrations on copper remained stable near 105 CFU/cm2 until day 50 and then decreased until day 90. Concentrations on brass increased seven-fold to a maximum of 7.6 × 105 CFU/cm2 by day 14, and then steadily decreased until day 90. Concentrations on polyvinyl chloride (PVC) followed a similar trend to brass, increasing to 1.6 × 105 CFU/cm2 by day 21 before decreasing. Final concentrations on copper, brass, and PVC were similar at day 90, each near 104 CFU/cm2, approximately a 1-log reduction from the initial spiked concentrations. Legionella levels in water surrounding each coupon (Figure 3) eventually decreased, with final concentrations of 1.3 × 103, 2.1 × 103, 4.9 × 103, and 4.9 × 103 CFU/mL for brass, cast iron, copper, and PVC, respectively. Concentrations were stable for 3, 8, 8, and 14 days in water surrounding the cast iron, copper, brass, and PVC coupons, respectively.


Impact of environmental factors on legionella populations in drinking water.

Schwake DO, Alum A, Abbaszadegan M - Pathogens (2015)

L. pneumophila concentrations in biofilms on coupons submerged in tap water incubated at 25 °C. Error bars indicate standard error between duplicate samples of each culture.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493474&req=5

pathogens-04-00269-f002: L. pneumophila concentrations in biofilms on coupons submerged in tap water incubated at 25 °C. Error bars indicate standard error between duplicate samples of each culture.
Mentions: For all pipe materials, similar Legionella biofilm association (105 to 2.7 × 105 CFU/cm2) was observed three days after inoculation (Figure 2). After the initial three days, concentrations in biofilms formed on cast iron decreased before stabilizing at 1.2 × 103 CFU/cm2 for the duration of the study, resulting in a 2-log reduction. Concentrations on copper remained stable near 105 CFU/cm2 until day 50 and then decreased until day 90. Concentrations on brass increased seven-fold to a maximum of 7.6 × 105 CFU/cm2 by day 14, and then steadily decreased until day 90. Concentrations on polyvinyl chloride (PVC) followed a similar trend to brass, increasing to 1.6 × 105 CFU/cm2 by day 21 before decreasing. Final concentrations on copper, brass, and PVC were similar at day 90, each near 104 CFU/cm2, approximately a 1-log reduction from the initial spiked concentrations. Legionella levels in water surrounding each coupon (Figure 3) eventually decreased, with final concentrations of 1.3 × 103, 2.1 × 103, 4.9 × 103, and 4.9 × 103 CFU/mL for brass, cast iron, copper, and PVC, respectively. Concentrations were stable for 3, 8, 8, and 14 days in water surrounding the cast iron, copper, brass, and PVC coupons, respectively.

Bottom Line: Chlorination of the system had a greater effect on biofilm-associated Legionella concentrations, with populations returning to pre-chlorination levels within six weeks.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.

View Article: PubMed Central - PubMed

Affiliation: School of Life Sciences, Arizona State University, Tempe, AZ 85281, USA. david.schwake@asu.edu.

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.

No MeSH data available.