Close Genetic Relationship between Legionella pneumophila Serogroup 1 Isolates from Sputum Specimens and Puddles on Roads, as Determined by Sequence-Based Typing

Abstract

ABSTRACTWe investigated the prevalence ofLegionellaspecies isolated from puddles on asphalt roads. In addition, we carried out sequence-based typing (SBT) analysis on the genetic relationship betweenL. pneumophilaserogroup 1 (SG 1) isolates from puddles and from stock strains previously obtained from sputum specimens and public baths. Sixty-nine water samples were collected from puddles on roads at 6 fixed locations.Legionellaspecies were detected in 33 samples (47.8%) regardless of season. Among the 325 isolates from puddles, strains ofL. pneumophilaSG 1, a major causative agent of Legionnaires' disease, were the most frequently isolated (n= 62, 19.1%). Sixty-two isolates ofL. pneumophilaSG 1 from puddles were classified into 36 sequence types (STs) by SBT. ST120 and ST48 were identified as major STs. Environmental ST120 strains from puddles were found for the first time in this study. Among the 14 STs of the clinical isolates (n= 19), 4 STs (n= 6, 31.6%), including ST120, were also detected in isolates from puddles on roads, and the sources of infection in these cases remained unclear. Thelag-1gene, a tentative marker for clinical isolates, was prevalent in puddle isolates (61.3%). Our findings suggest that puddles on asphalt roads serve as potential reservoirs forL. pneumophilain the environment.