ABSTRACT
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 germiculture 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.