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Water Quality Influences Legionella pneumophila Determination
Citation:
Donohue, M., M. Pham, S. Brown, K. Easwaran, S. Vesper, AND J. Mistry. Water Quality Influences Legionella pneumophila Determination. WATER RESEARCH. Elsevier Science Ltd, New York, NY, 238:119989, (2023). https://doi.org/10.1016/j.watres.2023.119989
Impact/Purpose:
Context: Legionella pneumophila is the etiologic agent responsible for causing >90% of legionellosis cases in the United States. Legionellosis transmission primarily happens by the inhalation or aspiration of contaminated water aerosols or droplets. Therefore, methods are needed to detect and enumerate L. pneumophila in water. Method: Two hundred and nine potable water samples were collected from taps in buildings. Legionella pneumophila was measured by three methods, including the International Organization for Standardization (ISO) 11731 /Standard Methods (SM) 9260 J (Legionella) -filtration with washing procedure, Legiolert® 10- and 100-mL tests, and qPCR. Culture and molecular positive results were confirmed by secondary testing. In addition, eight water quality variables were recorded and measured, including source water type, secondary disinfectant, total chlorine residual, heterotrophic bacteria, total organic carbon, pH, water hardness, and cold- and hot-water lines. These eight variables were segmented into 28 categories to evaluate each method's performance. Results: Legionella pneumophila positive detection frequency ranged from 2 to 22%. The culture method parameters of sensitivity, specificity, positive and negative predictive value (PPV NPV), and tests’ accuracy ranged from 40 to 100%. The qPCR method parameters were >98% for sensitivity, specificity, PPV, NPV, and accuracy. Each method’s true to false positive ratio was evaluated in the 28 water quality sub-categories. The ISO method performed well in 54% (15/28). In comparison, the Legiolert® 10- and -100 mL products performed well in 18% (5/28) and 11% (3/28) water quality variables, respectively. The qPCR test was not affected by the water’s water quality,100% (28/28). The culture method’s false negative results frequently occurred in groundwater, high TOC (<2 mg/L), chloraminated water, and water with high amounts of heterotrophic bacteria (> 100 CFU/ml). The qPCR method had one false negative result. Conclusion: In order to receive the most accurate results in detecting L. pneumophila, method selection should consider the following: the water environment (water quality), the context of the situation (disease-associated or not), and the purpose of testing (general monitoring or determining the source of a legionellosis case).
Description:
Context: Legionella pneumophila is the etiologic agent responsible for causing >90% of legionellosis cases in the United States. Legionellosis transmission primarily happens by the inhalation or aspiration of contaminated water aerosols or droplets. Therefore, methods are needed to detect and enumerate L. pneumophila in water. Method: Two hundred and nine potable water samples were collected from taps in buildings. Legionella pneumophila was measured by three methods, including the International Organization for Standardization (ISO) 11731 /Standard Methods (SM) 9260 J (Legionella) -filtration with washing procedure, Legiolert® 10- and 100-mL tests, and qPCR. Culture and molecular positive results were confirmed by secondary testing. In addition, eight water quality variables were recorded and measured, including source water type, secondary disinfectant, total chlorine residual, heterotrophic bacteria, total organic carbon, pH, water hardness, and cold- and hot-water lines. These eight variables were segmented into 28 categories to evaluate each method's performance. Results: Legionella pneumophila positive detection frequency ranged from 2 to 22%. The culture method parameters of sensitivity, specificity, positive and negative predictive value (PPV NPV), and tests’ accuracy ranged from 40 to 100%. The qPCR method parameters were >98% for sensitivity, specificity, PPV, NPV, and accuracy. Each method’s true to false positive ratio was evaluated in the 28 water quality sub-categories. The ISO method performed well in 54% (15/28). In comparison, the Legiolert® 10- and -100 mL products performed well in 18% (5/28) and 11% (3/28) water quality variables, respectively. The qPCR test was not affected by the water’s water quality,100% (28/28). The culture method’s false negative results frequently occurred in groundwater, high TOC (<2 mg/L), chloraminated water, and water with high amounts of heterotrophic bacteria (> 100 CFU/ml). The qPCR method had one false negative result. Conclusion: In order to receive the most accurate results in detecting L. pneumophila, method selection should consider the following: the water environment (water quality), the context of the situation (disease-associated or not), and the purpose of testing (general monitoring or determining the source of a legionellosis case).
URLs/Downloads:
DOI: Water Quality Influences Legionella pneumophila Determination
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