Objective: To analyze the pollution status and influencing factors of Legionella pneumophila in a secondary water supply facility in a city. Methods: From June to August 2020, a survey on the level of Legionella pneumophila in secondary water supply unit was carried out in a city in northern China, and 304 sets of secondary water supply facilities were included in the study. A total of 760 water samples were collected from the inlet and outlet water of the secondary water supply facilities and some water samples in the water tank were collected for the detection of Legionella pneumophila, standard plate-count bacteria and related physical and chemical indicators. Through questionnaire survey, the basic information of secondary water supply facilities and daily management of water quality were collected. Multivariate logistic regression model was used to analyze the influencing factors of Legionella pneumophila contamination. Results: Among 304 sets of secondary water supply facilities, most of them were located in residential buildings [57.24% (174/304)]. High and low water tank water supply, low water tank variable frequency conversion water supply and non-negative pressure water supply accounted for 26.6% (81/304), 36.8% (112/304) and 36.5% (111/304), respectively. About 25.7% of facilities (78/304) were positive for Legionella pneumophila. Among them, the positive rates of Legionella pneumophila in high and low water tank water supply, low water tank variable frequency conversion water supply and non-negative pressure water supply facilities were 38.3% (31/81), 29.5% (33/112) and 12.6% (14/111), respectively. The results of multivariate logistic regression model analysis showed that the disinfectant residue could reduce the risk of Legionella pneumophila contamination in water samples, and the OR (95%CI) value was 0.083 (0.022-0.317). The increase of the standard plate-count bacteria and conductivity might increase the risk of Legionella pneumophila contamination in water samples. The OR (95%CI) values were 3.160 (1.667-5.99) and 1.004 (1.001-1.006), respectively. Compared with the non-negative pressure water supply, the risk of Legionella pneumophila contamination of secondary water supply facilities was increased by water supply from high and low water tanks and variable frequency conversion water supply from low water tanks, with OR (95%CI) values of 4.296 (2.096-8.803) and 2.894 (1.449-5.782), respectively. Conclusion: The positive rate of Legionella pneumophila in secondary water supply in the study city is high. Disinfectant residue, conductivity and method of water supply are associated with the positive rate of Legionella pneumophila.
目的： 分析中国某城市二次供水设施嗜肺军团菌的污染现状及其影响因素。 方法： 于2020年6—8月，对中国北方某城市二次供水单位开展嗜肺军团菌污染水平调查，将304套二次供水设施纳入研究。采集二次供水设施的进水、出水和部分水箱水共760份水样进行嗜肺军团菌、菌落总数和相关理化指标检测；通过问卷调查收集二次供水设施基本情况和水质日常管理情况等，采用多因素logistic 回归模型分析嗜肺军团菌污染的影响因素。 结果： 304套二次供水设施中，设置在居民楼的占比较高［57.24%（174/304）］；高低位水箱供水、低位水箱变频供水和无负压供水分别占26.6%（81/304）、36.8%（112/304）和36.5%（111/304）；25.7%的设施（78/304）嗜肺军团菌阳性，其中高低位水箱供水、低位水箱变频供水和无负压供水设施的嗜肺军团菌阳性率分别为38.3%（31/81）、29.5%（33/112）和12.6%（14/111）。多因素 logistic回归模型分析结果显示，提高消毒剂余量会降低水样被嗜肺军团菌污染的风险，OR（95%CI）值为0.083（0.022~0.317），菌落总数、电导率升高会增加水样被嗜肺军团菌污染的风险，OR（95%CI）值分别为3.160（1.667~5.99）、1.004（1.001~1.006）；与无负压供水方式相比，高低位水箱供水、低位水箱变频供水会导致二次供水设施被嗜肺军团菌污染的风险增加，OR（95%CI）值分别为4.296（2.096~8.803）、2.894（1.449~5.782）。 结论： 中国某城市二次供水中的嗜肺军团菌阳性率较高；消毒剂余量、菌落总数、电导率等参数和二次供水设施的供水形式与嗜肺军团菌阳性有关联。.