Population Genetics Analysis Of Legionella Pneumophila Isolated From Guangzhou By Using

Legionella pneumophila is ubiquitous in nature aquatic environment, such as river, lake, cooling tower, air-conditioning evaporative condensers, humidifiers, fountain,etc. L. pneumophila is an intracellular pathogen causes Legionnaires’disease (LD) or Legionellosis. Human inhalations of Legionella-contaminated aerosols will cause Legionnaires’ disease(LD), Legionella infections are sporadic, sometimes invoke Community-Acquired Pneumonia. In this study, we analyze116isolates from Guangzhou city by sequence based typing (SBT). The purpose of this study was to gain insights of the population structure of L. pneumophila in Guangzhou city, and provides data to decipher the Legionnaires’ disease epidemiology in this region.Briefly, seven genes of L.pneumophila were amplified and sequenced, then the sequence results were input into Bionumerics6.6to get the allele profiles and STs(sequence type,ST). Based on the allele profiles and STs, software Bionumerics6.6, eBURST, START2.0, SplitsTree4.0, RDP3.0, ClonalFrame were employed to portrait the population structure of the test strains. In this study, the116isolates were assigned into30sequence types (STs),16of which were novel STs in the SBT databases of the European Working Group for Legionella Infections (EWGLI). Two clonal complex (CCs) were identified in8STs out of30STs, the remaining22as STs singleton, ST1is the dominating ST and was identified as the founder of CC1via the eBURST V3program. Linkage disequilibrium analyses by START2.0revealed IAs as0.3259(p<0.001) for30STs, while0.6969(p<0.001) for all the116isolates. Based on the concatenated sequences of all isolates STs, isolates from Gungzhou presents a split network structure with considerable parallelogram formation revealed by the SplitsTree4.0. ClonalFrame calculated the ratio of r/m=0.9(0.95%confidence interval [0.2-1.9]) based on the30STs. RDP3.0were used to identified the recombination events based on the116isolates and30STs concatenated sequences, and the number of potential recombination events were3and5, respectively. Using the databases of EWGLI, we also analyzed the population structure of global L. pneumophila isolates in the world. In conclusion, we set the population structure of L. pneumophila as clonal overall.