Objective To investigate Legionella pneumophila pollution in public air-conditioning cooling water and condensate water in Songjiang District of Shanghai, and provide a basis for the prevention of legionnaires' disease.

Methods A total of 66 samples of air-conditioning cooling water and condensate water were collected from 8 hotels, 7 supermarkets, and 8 office buildings from July to October in 2015. PCR technique and routine microorganism identification technique were applied. Serological identification was also carried out.

Results The positive rate of Legionella pneumophila was 51.6% in cooling water samples by the routine technique and 58.3% by PCR. The positive rate of Legionella pneumophila was 11.4% in condensate water samples by the routine technique and 14.3% by PCR. Higher positive rates in cooling water than in condensate water were shown by the two techniques, and the difference was statistically significant (P < 0.01). There were five different serological types identified, with LP1 as the major one, accounting for 73.9%. The proportion of two types identified in one sample was 13.0%. No statistical differences were shown by the two methods. The difference in positive rates of Legionella pneumophila was not statistically significant among hotels, supermarkets, and office buildings.

Conclusion Legionella pneumophila contamination exists in air-conditioning systems in public places in Songjiang District. Attention needs to be paid to the supervision of air-conditioning systems in public places for the sake of preventing Legionella pneumophila outbreak and prevalence.