空调循环水系统军团菌微生态与其存活力研究
Microecoenvironment of Legionella pneumophila with its Vitality Overwintering in Air-conditioning Cooling Tower
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摘要:
目的 探讨冬季军团菌在空调循环水系统中的微生态环境与其存活力的关系。寻找军团菌在空调循环水系统中的越冬场所及其赖以生存的相关因素, 为阻断军团菌在空调冷却塔中繁殖、传播提供依据。 方法 选择 8月份军团菌数高的空调冷却塔作现场调查, 同时模拟空调冷却塔条件, 构建藻类减少和藻类增加两种不同的军团菌生态模型。定期分别采集水样和沉积在容器表面的地衣 -藻类混合体作军团菌检测和扫描电镜观察, 并对水样中的藻体数、总有机碳和硝酸盐氮等进行检测。 结果 10月下旬, 空调机关机后, 冷却塔水样中无军团菌检出, 但在地衣 -藻类混合体中检测到高达 104 CFU/4 cm2的军团菌, 扫描电镜观察发现藻类混合体的外膜上附着有较多的杆菌和军团菌。12月底, 藻类减少模型无军团菌检出, 但冷却塔和藻类增加模型均有检出。次年 2月下旬, 冷却塔和藻类减少模型中均无检出, 只有藻类增加模型有检出。扫描电镜观察发现, 12月底可观察到有节的丝状藻类, 个别的军团菌附着于藻壁上。次年 2月下旬, 则绝大多数为地衣的纤维状组织、霉菌及其菌丝体。 结论 空调冷却塔底部地衣 -藻类混合体是军团菌越冬的场所。四棘藻和地中尖头藻这类丝状藻类的细胞壁可能是军团菌越冬赖以生存的营养物。空调器关机时地衣和藻类数越少, 循环水不流动的时间越长, 军团菌在循环水管道系统中度过冬季的可能性越少。 Abstract:Objective To explore microecoenvironment of Legionella pneumophila with its vitality overwintering and to provide reference for preventing proliferation and propagation of Legionella pneumophila in air-conditioning cooling tower. Methods Two air-conditioning cooling towers with numerous Legionella pneumophila in August were selected to perform spot investigation, meanwhile the environment of cooling tower was imitated to constitute two different ecopatterns of Legionella pneumophila, in which the water and lichen-alga mixture on container surface were periodically and respectively sampled for Legionella pneumophila detection and scanning electron microscope observation. The concentration of total organic carbon (TOC), No3--N and alga in water sample were also tested. Results In late October, after the air-conditioner was turned off, no Legionella pneumophila was detected in the water sample but as much as 104 CFU/4 cm2 in the lichen-alga mixture, on the biomembrane of which numerous Legionella pneumophila was observed under scanning electron microscope. In the end of December, Legionella pneumophila was not detected in the alga reduction ecopattern but was detected in the cooling tower and the alga addition ecopattern. In the end of February next year, Legionella pneumophila was not detected in the cooling tower and the alga reduction ecopattern but was detected in alga addition ecopattern. Under scanning electron microscope it was observed that a couple of Legionella pneumophila adhered to the wall of filiform alga in the end of December, but at the end of February next year there was only fungi and its mycelium. Conclusion It is suggested that the lichen-alga mixture on container surface is the overwintering refuge for Legionella pneumophila which probably gain nutrition from the biomembrane of filiform alga. The fewer algae exist when air-conditioner is turned off and the longer circulating water keeps still, the less the possibility of Legionella pneumophila living through winter will be.
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