Sequence based typing of Legionella pneumophila serotype 1 isolated from natural environment in China, 2008-2012

Objective To understand the genotype and population structure of Legionella pneumophila serogroup 1 isolates from natural environment in China. Methods Sequence-based typing (flaA, pile, asd, mip, mompS, proA, neuA) was conducted to analyze 206 strains of L. pneumophila serogroup 1 isolated from different environments in China. Results Fifty-four STs were obtained with an index of discrimination (IOD) of 0.7205. The 49 hot spring isolates were classified into 25 STs (IOD=0.9498), the 130 cooling tower isolates were classified into 31 STs (IOD=0.6453), and the 27 potable water isolates were classified into 3 STs (IOD=0.1453). For seven SBT loci, Nei's index were 0.7721-0.8563, 0.4227-0.4970, and 0.1425-0.1453 for hot spring, cooling tower, and potable water isolates respectively. Fifty-four STs were predicted to form five complexes. The comparison between the strains isolated in China and the strains isolated in other countries revealed that similar clones (ST1 complex) exist in these countries. Conclusion In China, the STs of L. pneumophila serogroup 1 had highly complex gene polymorphism and population structure, and ST1 was the most predominant sequence type of environmental L. pneumophila serogroup 1 isolates obth in China and in the world.