United States Environmental Protection Agency, Cincinnati, OH 45268, USA.
United States Environmental Protection Agency, Cincinnati, OH 45268, USA.
Water Res. 2023 Jun 30;238:119989. doi: 10.1016/j.watres.2023.119989. Epub 2023 Apr 25.
Legionellosis is a respiratory disease of public health concern. The bacterium Legionella pneumophila is the etiologic agent responsible for >90% of legionellosis cases in the United States. Legionellosis transmission primarily occurs through the inhalation or aspiration of contaminated water aerosols or droplets. Therefore, a thorough understanding of L. pneumophila detection methods and their performance in various water quality conditions is needed to develop preventive measures. Two hundred and nine potable water samples were collected from taps in buildings across the United States. L. pneumophila was determined using three culture methods: Buffered Charcoal Yeast Extract (BCYE) culture with Matrix-assisted Laser Desorption/Ionization Mass Spectrometry (MALDI-MS) identification, Legiolert® 10- and 100-mL tests, and one molecular method: quantitative Polymerase Chain Reaction (qPCR) assay. Culture and molecular positive results were confirmed by secondary testing including MALDI-MS. Eight water quality variables were studied, including source water type, secondary disinfectant, total chlorine residual, heterotrophic bacteria, total organic carbon (TOC), pH, water hardness, cold- and hot-water lines. The eight water quality variables were segmented into 28 categories, based on scale and ranges, and method performance was evaluated in each of these categories. Additionally, a Legionella genus qPCR assay was used to determine the water quality variables that promote or hinder Legionella spp. occurrence. L. pneumophila detection frequency ranged from 2 to 22% across the methods tested. Method performance parameters of sensitivity, specificity, positive and negative predictive values, and accuracy were >94% for the qPCR method but ranged from 9 to 100% for the culture methods. Water quality influenced L. pneumophila determination by culture and qPCR methods. L. pneumophila qPCR detection frequencies positively correlated with TOC and heterotrophic bacterial counts. The source water-disinfectant combination influenced the proportion of Legionella spp. that is L. pneumophila. Water quality influences L. pneumophila determination. To accurately detect L. pneumophila, method selection should consider the water quality in addition to the purpose of testing (general environmental monitoring versus disease-associated investigations).
军团病是一种公共卫生关注的呼吸道疾病。在美国，超过 90%的军团病病例由嗜肺军团菌引起。军团病的传播主要通过吸入或吸入受污染的水气溶胶或飞沫。因此，需要深入了解嗜肺军团菌的检测方法及其在各种水质条件下的性能，以制定预防措施。从美国各地的建筑物水龙头采集了 209 份饮用水样本。使用三种培养方法确定嗜肺军团菌：缓冲木炭酵母提取物（BCYE）培养，基质辅助激光解吸/电离质谱（MALDI-MS）鉴定，Legiolert® 10 和 100-mL 测试，以及一种分子方法：定量聚合酶链反应（qPCR）检测。培养和分子阳性结果通过包括 MALDI-MS 在内的二次检测进行确认。研究了八个水质变量，包括水源类型、二次消毒剂、总余氯、异养菌、总有机碳（TOC）、pH 值、水硬度、冷热水线。根据规模和范围，将这八个水质变量分为 28 个类别，并在每个类别中评估方法性能。此外，还使用军团菌属 qPCR 检测法确定促进或阻碍军团菌属发生的水质变量。在测试的方法中，嗜肺军团菌的检测频率范围为 2%至 22%。qPCR 方法的灵敏度、特异性、阳性和阴性预测值以及准确性等性能参数均>94%，而培养方法的范围则为 9%至 100%。水质会影响通过培养和 qPCR 方法对嗜肺军团菌的检测。嗜肺军团菌 qPCR 检测频率与 TOC 和异养菌计数呈正相关。水源-消毒剂组合影响军团菌属中嗜肺军团菌的比例。水质会影响嗜肺军团菌的检测。为了准确检测嗜肺军团菌，除了测试目的（一般环境监测与疾病相关调查）外，还应考虑水质选择方法。
