Abstract: Objective To study the characteristics of contamination changes of Legionella pneumophila in the cooling tower water of a subway in a city in Hubei Province using Legiolert and isolation culture method,and to evaluate the effectiveness of existing hygiene management measures in controlling Legionella pneumophila. Methods According to the service life of the cooling tower,3 phases lines were randomly selected from the 21 phase lines of a city. From July 2021 to June 2022,during one operating cycle of the cooling tower,researchers from the Wuhan Centers for Disease Control and Prevention sampled all the cooling tower water of the third phase of the project line and conducted simultaneous detection of Legionella pneumophila using Legiolert and isolation culture method. Results There were no statistically significant differences in the detection rate of Legionella pneumophila in cooling towers with long service life within one operating（At the early,middle,and end of operation,the detection rates of the isolation culture method were 36.8%,52.6%,and 68.4%,respectively, χ²_{isolation culture method}=3.800,P>0.05,and the detection rates of Legiolert were 57.9%,52.6%,and 57.9%,respectively, χ²_Legiolert=0.143,P>0.05）. There were statistically significant differences in the detection rate of Legionella pneumophila in cooling towers with medium service life within one operating（At the early,middle,and end of operation,the detection rates of isolation culture method were 4.3%,78.3%,and 73.9%,respectively,χ²_{isolation culture method}=31.712,P<0.05,and the detection rates of Legiolert were 4.3%,91.3%,and 100.0%,respectively, χ²_Legiolert=56.733,P<0.05）. There were statistically significant differences in the detection rate of Legionella pneumophila in cooling towers with shorter service life within one operating（At the early,middle,and end of operation,the detection rates of isolation culture method were 18.8%,81.3%, and 43.8%,respectively, χ²_{isolation culture method}=12.689,P<0.05,and the detection rates of Legiolert were 18.8%,87.5%,and 81.3%,respectively, χ²_Legiolert=19.733,P<0.05）. The detection rate of Legionella pneumophila in cooling towers with medium service life and short service life was lower in the early of operation,but increased in the middle and end of operation. In the middle and end of cooling tower operation,the concentration level of Legionella pneumophila in the cooling tower water of the third phase line tended to be consistent（ χ²_{middle of cooling tower operation}=1.015, χ²_{end of cooling tower operation}=3.198,both P>0.05）. Compared with before the implementation of hygiene management intervention measures,the existing hygiene management measures had a certain inhibitory effect on the proliferation of Legionella pneumophila in cooling towers,but could not completely solve the pollution problem（Cooling towers with long service life：The concentration of Legionella pneumophila before intervention was 338 973.876 MPN/mL,and the concentration of Legionella pneumophila after intervention was 5.200 MPN/mL,Z=-5.309,P<0.05. Cooling towers with medium service life：The concentration of Legionella pneumophila before intervention was 257 992.739 MPN/mL,and the concentration of Legionella pneumophila after intervention was 65.900 MPN/mL,Z=-5.330,P<0.05. Cooling towers with shorter service life：The concentration of Legionella pneumophila before intervention was 278 252.443 MPN/mL,and the concentration of Legionella pneumophila after intervention was 110.650 MPN/mL,Z=-4.827,P<0.05）. Conclusion The cooling tower of a subway in a certain city in Hubei Province with a long service life has serious contamination of Legionella pneumophila in the cooling tower water,and shows a long-term pollution trend. The contamination of Legionella pneumophila in cooling towers with medium to short service life is related to the operation period of the cooling tower,and the pollution is extremely severe during the middle and late stages of the cooling tower operation. The existing hygiene management measures have a certain inhibitory effect on the proliferation of Legionella pneumophila in cooling towers,but have not completely solved the pollution problem.

Key words: Subway, Cooling tower, Legionella pneumophila, Isolation culture method, Legiolert