Objective To study the risk factors of Legionella pneumophila contamination in public fountains, establish a logistic regression model for predicting the contamination, and provide a scientific basis for related prevention and control.
Methods Eighty functioning public fountains were selected in Shenzhen. Data were collected using questionnaire survey, field test, and laboratory test. The data collected from 50 fountains (including 30 fountains in residence communities and 20 fountains surrounding public buildings) from July to December 2015 were used to establish a logistic regression model to assess the associations between Legionella pneumophila contamination and selected influencing factors, and then a receiver operating characteristic curve (ROC curve) was drawn to determine the optimal threshold of Legionella pneumophila contamination for the model. The data from 30 fountains (including 20 fountains in residence communities and 10 fountains surrounding public buildings) were collected from January to July 2016 to validate the accuracy of the model.
Results The results of univariate logistic regression analysis showed that the increased level of free residual chlorine was a protective factor for Legionella pneumophila contamination in fountains (OR=0.986); whereas the increased operating years, turbidity, and total dissolved solids were risk factors (OR=1.096, 1.261, 1.100). According to multivariate logistic regression analysis, the independent factors predicting Legionella pneumophila contamination were free residual chlorine (OR=0.952, P<0.05), turbidity (OR=1.314, P<0.05), and total dissolved solids (OR=1.098, P<0.05). The area under the ROC curve was 0.877 (95%CI:0.808-0.997) and the prediction accuracy rate of the model was 80.0%.
Conclusion Free residual chlorine, turbidity, and total dissolved solids are the main risk factors of Legionella pneumophila contamination in the logistic regression model. The model with a high accuracy could provide reference for predicting Legionella pneumophila contamination in fountains in public places.
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