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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