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Effect of Common Drinking Water Disinfectants, Chlorine and Heat, on Free Legionella and Amoebae-Associated Legionella.

Cervero-Aragó S, Rodríguez-Martínez S, Puertas-Bennasar A, Araujo RM - PLoS ONE (2015)

Bottom Line: Inactivation models obtained were used to determine the effectiveness of the treatments applied which resulted more effective against Legionella than Acanthamoeba, especially those in cystic stages.The Legionella-amoeba association did not change the inactivation models, but it reduced the effectiveness of the treatments applied.Remarkably, at the lowest free chlorine concentration, 0.5 mg L-1, as well as at the lowest temperatures, 50°C and 55°C, the influence of the Legionella-amoeba associate state was the strongest in reducing the effectiveness of the treatments compared to the free Legionella state.

View Article: PubMed Central - PubMed

Affiliation: Departament de Microbiologia, Facultat de Biologia, Universitat de Barcelona, Av. Diagonal 643, 08028, Barcelona, Spain; Water Hygiene, Institute for Hygiene and Applied Immunology, Medical University of Vienna, Kinderspitalgasse 15, A-1090, Vienna, Austria.

ABSTRACT
Chlorine and thermal treatments are the most commonly used procedures to control and prevent Legionella proliferation in drinking water systems of large buildings. However, cases of legionellosis still occur in facilities with treated water. The purpose of this work was to model the effect of temperature and free chlorine applied in similar exposure conditions as in drinking water systems on five Legionella spp. strains and two amoebal strains of the genera Acanthamoeba. Inactivation models obtained were used to determine the effectiveness of the treatments applied which resulted more effective against Legionella than Acanthamoeba, especially those in cystic stages. Furthermore, to determine the influence of the relationship between L. pneumophila and Acanthamoeba spp. on the treatment effectiveness, inactivation models of the bacteria-associated amoeba were also constructed and compared to the models obtained for the free living bacteria state. The Legionella-amoeba association did not change the inactivation models, but it reduced the effectiveness of the treatments applied. Remarkably, at the lowest free chlorine concentration, 0.5 mg L-1, as well as at the lowest temperatures, 50°C and 55°C, the influence of the Legionella-amoeba associate state was the strongest in reducing the effectiveness of the treatments compared to the free Legionella state. Therefore, the association established between L. pneumophila and amoebae in the water systems indicate an increased health risk in proximal areas of the system (close to the tap) where lower free chlorine concentrations and lower temperatures are commonly observed.

No MeSH data available.


Related in: MedlinePlus

Effect of thermal treatments on the inactivation of 5 Legionella strains.Bacterial inactivation was determined using viable counts on BCYE agar medium. Data are presented as means ± SD (columns and error bars; n = 3). Statistical differences between means within each time point were represented assigning different letters to the bar plot. The same letter was assigned to bars with no significant differences between them. Statistical analyses were performed by ANOVA and pairwise Fisher’s LSD test (p<0.05).
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pone.0134726.g003: Effect of thermal treatments on the inactivation of 5 Legionella strains.Bacterial inactivation was determined using viable counts on BCYE agar medium. Data are presented as means ± SD (columns and error bars; n = 3). Statistical differences between means within each time point were represented assigning different letters to the bar plot. The same letter was assigned to bars with no significant differences between them. Statistical analyses were performed by ANOVA and pairwise Fisher’s LSD test (p<0.05).

Mentions: A thermal treatment at five different temperatures, 50°C, 55°C, 60°C, 65°C and 70°C, was applied to the five Legionella spp. strains. The results showed significant differences between the inactivation patterns of the five strains, especially L. longbeachae ATCC 33462, which was significantly (p<0.001) the most sensitive to all the thermal treatments applied. Significant differences (p<0.05) were found among the rest of the strains used, but the behavior of each strain varied depending of the thermal treatment applied (Fig 3).


Effect of Common Drinking Water Disinfectants, Chlorine and Heat, on Free Legionella and Amoebae-Associated Legionella.

Cervero-Aragó S, Rodríguez-Martínez S, Puertas-Bennasar A, Araujo RM - PLoS ONE (2015)

Effect of thermal treatments on the inactivation of 5 Legionella strains.Bacterial inactivation was determined using viable counts on BCYE agar medium. Data are presented as means ± SD (columns and error bars; n = 3). Statistical differences between means within each time point were represented assigning different letters to the bar plot. The same letter was assigned to bars with no significant differences between them. Statistical analyses were performed by ANOVA and pairwise Fisher’s LSD test (p<0.05).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4524690&req=5

pone.0134726.g003: Effect of thermal treatments on the inactivation of 5 Legionella strains.Bacterial inactivation was determined using viable counts on BCYE agar medium. Data are presented as means ± SD (columns and error bars; n = 3). Statistical differences between means within each time point were represented assigning different letters to the bar plot. The same letter was assigned to bars with no significant differences between them. Statistical analyses were performed by ANOVA and pairwise Fisher’s LSD test (p<0.05).
Mentions: A thermal treatment at five different temperatures, 50°C, 55°C, 60°C, 65°C and 70°C, was applied to the five Legionella spp. strains. The results showed significant differences between the inactivation patterns of the five strains, especially L. longbeachae ATCC 33462, which was significantly (p<0.001) the most sensitive to all the thermal treatments applied. Significant differences (p<0.05) were found among the rest of the strains used, but the behavior of each strain varied depending of the thermal treatment applied (Fig 3).

Bottom Line: Inactivation models obtained were used to determine the effectiveness of the treatments applied which resulted more effective against Legionella than Acanthamoeba, especially those in cystic stages.The Legionella-amoeba association did not change the inactivation models, but it reduced the effectiveness of the treatments applied.Remarkably, at the lowest free chlorine concentration, 0.5 mg L-1, as well as at the lowest temperatures, 50°C and 55°C, the influence of the Legionella-amoeba associate state was the strongest in reducing the effectiveness of the treatments compared to the free Legionella state.

View Article: PubMed Central - PubMed

Affiliation: Departament de Microbiologia, Facultat de Biologia, Universitat de Barcelona, Av. Diagonal 643, 08028, Barcelona, Spain; Water Hygiene, Institute for Hygiene and Applied Immunology, Medical University of Vienna, Kinderspitalgasse 15, A-1090, Vienna, Austria.

ABSTRACT
Chlorine and thermal treatments are the most commonly used procedures to control and prevent Legionella proliferation in drinking water systems of large buildings. However, cases of legionellosis still occur in facilities with treated water. The purpose of this work was to model the effect of temperature and free chlorine applied in similar exposure conditions as in drinking water systems on five Legionella spp. strains and two amoebal strains of the genera Acanthamoeba. Inactivation models obtained were used to determine the effectiveness of the treatments applied which resulted more effective against Legionella than Acanthamoeba, especially those in cystic stages. Furthermore, to determine the influence of the relationship between L. pneumophila and Acanthamoeba spp. on the treatment effectiveness, inactivation models of the bacteria-associated amoeba were also constructed and compared to the models obtained for the free living bacteria state. The Legionella-amoeba association did not change the inactivation models, but it reduced the effectiveness of the treatments applied. Remarkably, at the lowest free chlorine concentration, 0.5 mg L-1, as well as at the lowest temperatures, 50°C and 55°C, the influence of the Legionella-amoeba associate state was the strongest in reducing the effectiveness of the treatments compared to the free Legionella state. Therefore, the association established between L. pneumophila and amoebae in the water systems indicate an increased health risk in proximal areas of the system (close to the tap) where lower free chlorine concentrations and lower temperatures are commonly observed.

No MeSH data available.


Related in: MedlinePlus