A Surveillance Study of Cooling Tower Water of Large Buildings in Seoul City for Legionella Species with Molecular Analysis / 감염

BACKGROUND: To prevent and control legionellosis outbreaks, it is important to monitor cooling towers for Legionella and establish epidemiological markers. We determined level of contamination with Legionella of cooling tower in Seoul city, analyzed the distribution of Legionella subtypes, and evaluated molecular typing methods for discrimination power and feasibility. METHODS: Water samples from 120 cooling towers in 25 areas(Gu) of Seoul city were collected during June, 1997. Culture and duplex-PCR(polymerase chain reaction) with Southern hybridization probed with Legionella-specific genes were performed with filtered samples. Twenty-two Legionella isolates were analyzed comparatively by pulsed-field gel electrophoresis(PFGE) and arbitrarily primed(AP)-PCR using a M13 reverse primer. RESULTS: Culture and duplex-PCR with Southern hybridization were positive for Legionella in 22(18.3%) and 106(88.3%) of 120 samples, respectively, resulting in 90.8%(109/120) of contamination level. Out of 22 Legionella isolates, 17 were identified as Legionella pneumophila serogroup 1, 4 as L. pneumophila serogroup 6 and 1 as an unknown. Molecular analysis of 17 isolates of L. pneumophila serogroup 1 showed 7 subtypes by PFGE(A0 in 9 isolates; A1, 2; A2, 1; A3, 2; B, 1; C, 1; D, 1) and 5 subtypes by AP-PCR(Ia in 11 isolates; Ib, 2; Ic, 2; II, 1; III, 1). The agreement of results of both methods was 76.5%(13/17) of L. pneumophila serogroup 1 and 81.8%(18/22) of all isolates, respectively. CONCLUSION: Most of cooling towers in Seoul city were already contaminated with Legionella just before summer, requiring decontamination measures and continuous surveillance. L. pneumophila serogroup 1 was the predominant isolate with variable subtypes. The AP-PCR can be used as a rapid and reproducible screening tool in tracking legionellosis outbreak.

Investigation on Sanitation Administration and Legionella pneumophila Contamination in Central Air Conditioning System of Public Places / 环境与健康杂志

Objective To know the hygienic administration status of central air conditioning system(CACS)and the Legionella contamination of cooling water in public places; and to identify the risk factors for legionella contamination associated with hygienic administration measures of CACS. Methods One hundred and forty-eight public places with CACS were recruited and the hygienic administration status was investigated by questionnaire survey in Sep. 2008. The culture methods were used to identify Legionella in cooling water. Results Positive rate of Legionella pneumophila in cooling water was 68.1%, 65.1% and 66.7% respectively in the condition of disinfection, preservative (detergent) and regular examination of the cooling water. The positive rate of Legionella pneumophila in cooling water was 92%, 87.7% and 84.7% respectively without disinfection, preservative,detergent and regular examination of the cooling water. Conclusion Disinfection, preservative,detergent and regular examination of the cooling water can reduce Legionella contamination risk.