中央空调冷却塔气溶胶军团菌污染研究

Study on Legionella Contamination in Aerosols from Cooling Towers in Central Air Conditioning System

目的了解中央空调冷却塔气溶胶军团菌污染状况和影响因素,探讨早期预警,研究有效的采集方法。方法于2008年6—8月对马鞍山市13户宾馆、商场、浴场当年使用的中央空调系统进行两轮采样;用液体撞击式微生物气溶胶采样器收集中央空调冷却塔气溶胶,同时采集同一系统的冷却塔、膨胀水箱水样,对67件样品分别用细菌培养法、聚合酶链反应法(PCR)检测军团菌。结果气溶胶军团菌培养阳性率为0,PCR检测阳性率为50.0%,采样容积≥400L和<400L的气溶胶样品检测阳性率分别为90.0%和16.7%,差异有统计学意义(χ2=11.7,P=0.001)。随着冷却塔运行时间的延长,气溶胶含菌阳性率升高,气溶胶检出军团菌组的现场相对湿度高于未检出组(P=0.002)。结论气溶胶军团菌的PCR检测结果阳性,应成为发生、传播军团病的重要的早期预警指征。收集400L以上空气可满足冷却塔气溶胶军团菌的PCR检测,高湿环境可增加军团菌污染气溶胶的风险。

Objective To explore and describe the sampling methods for aerosol from cooling towers in the centralized air conditioning system, early-warning indicators, the effect factor and present status of contamination by Legionella. Methods Air- conditioning systems were sampled two rounds in 13 guesthouses, markest and bathing spots of Maanshan City in June-August, 2008. Aerosols were collected by fluid-striking microbial aerosol sample collector, while water samples from cooling tower and swelling box were obtained. Legionella were determined respectively for 67 samples by germiculture and polymerase chain reaction. Results The positive rate of Legionella in aerosols by germicuhure was 0, meanwhile it was 50.0% by polymerase chain reaction for Legionella pneumophila. The positive rate in aerosols was 90.0% as the air-sampling volume exceeded 400 L. The positive rate of aerosols increased while the operating-time of cooling tower increased. The relative humidity in Legionella positive groups was higher than that in Legionella negative groups. Conclusion The positive result for Legionella pneumophila by polymerase chain reaction should be an important indicator for early-warning for the occurrence and spreading of Legionnaires＇ disease. The air-sampling volume of over 400 L is available by sampling collector for the detection of Legionella pneumophila by polymerase chain reaction. Risk of Legionella contamination in aerosol would be raised in high-humidity environment.