Journal of Water and Health (Nov 2023)
Prevalence and genetic distribution of Legionella spp. in public bath facilities in Kobe City, Japan
Abstract
Legionella is an important waterborne pathogen that causes legionellosis. Public baths are considered the primary cause of legionellosis infection in Japan. We investigated the prevalence and genetic distribution of 338 Legionella spp. isolates from 81 public bath facilities, including 35 hot springs and 46 other facilities, through annual periodic surveillance in Kobe, Japan, from 2016 to 2021. In addition, the genotypes of nine clinical strains of unknown infectious source from the same period were compared to those of bathwater isolates. We elucidated the differences in the distribution of Legionella species, serogroups, and genotypes between hot springs and other public baths. Legionella israelensis, L. londiniensis, and L. micdadei colonized hot springs along with L. pneumophila. The minimum spanning tree analysis based on multiple-locus variable number tandem repeat analysis (MLVA) also identified four major clonal complexes (CCs) in L. pneumophila SG1 and found that CC1 of the four CCs is a specific novel genotype with the lag-1 gene in hot springs. The same MLVA genotypes and sequence types as those of the clinical strains were not present among the strains isolated from bath water. Thus, our surveillance is useful for estimating the sources of legionellosis infection in Japan and developing prevention strategies. HIGHLIGHTS We elucidated differences in the distribution of Legionella species, serogroups, and genotypes between hot springs and other public baths.; 10 STs (ST-KB1-KB10) identified as unique types in this study had novel allelic profiles.; No strains from bath water in our samples exhibited the same MLVA genotypes or STs as the clinical strains collected through surveillance during the same period.; Our study will be useful for estimating the sources of infection in Japan and developing prevention strategies.;
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