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KMID : 0364820130490040424
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Korean Journal of Microbiology
2013 Volume.49 No. 4 p.424 ~ p.428
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Meta-Analysis of Risk Factors for Contamination of Environmental Waters by Legionella
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Zo Young-Gun
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Abstract
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To identify risk factors for Legionella contamination, water quality variables routinely measured in examination of
natural and city waters were meta-analyzed for significance of correlation to Legionella incidences. For evaluation
of abundance of Escherichia coli as a risk factor, which is currently used as an indicator of Legionella contamination
in an official guideline in Korea, odds ratio (OR) of above-cutoff total coliform counts for Legionella presence/absence was used as the effect size in the meta-analysis. The OR was estimated as 1.05 (0.36?3.12, 95% CI), and the probability of having identical odds reached 0.92. Also, ORs from individual studies showed significant heterogeneity (P=0.008), which contributed to 63% of total variance of the ORs. In the case of heterotrophic plate count (HPC), the OR for Legionella presence/absence was 2.72 (2.04?3.63) with highly significant deviation from identical odds (P<0.0001). ORs from different studies were seemingly homogeneous (Qdf=8=12.7, P=0.12). Turbidity and concentrations of chlorine, iron ion and cupper ion were other routine variables that could be considered as risk factors. However, statistical measures from different studies were not uniform enough to develop an appropriate effect size while the number of studies reporting the variables was also small (3?5). In conclusion, HPC appeared to be appropriate as indicator of Legionella contamination, rather than fecal bacteria contamination. HPC may imply abundance of habitats (amoebas and biofilms) of Legionella in water. This result warrants further studies for standardizing protocols and cutoff values to infer Legionella risks from HPC.
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KEYWORD
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Legionella, heterotrophic plate count, indicator, meta-analysis, water quality
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