title: High prevalence, genetic diversity and intracellular growth ability of Legionella in hot spring environments.
abstract: BACKGROUND
  Legionella is the causative agent of Legionnaires' disease, and hot springs are a major source of outbreaks of this disease. It is important from a public health perspective to survey hot spring environments for the presence of Legionella.
  
  
  METHODS
  Prospective surveillance of the extent of Legionella pollution was conducted at three hot spring recreational areas in Beijing, China in 2011. Pulsed-field gel electrophoresis (PFGE) and sequence-based typing (SBT) were used to describe the genetic polymorphism of isolates. The intracellular growth ability of the isolates was determined by interacting with J774 cells and plating the dilutions onto BCYE agar plates.
  
  
  RESULTS
  Overall, 51.9% of spring water samples showed Legionella-positive, and their concentrations ranged from 1 CFU/liter to 2,218 CFU/liter. The positive rates of Legionella were significantly associated with a free chlorine concentration of ≥0.2 mg/L, urea concentration of ≥0.05 mg/L, total microbial counts of ≥400 CFU/ml and total coliform of ≥3 MPN/L (p<0.01). The Legionella concentrations were significantly associated with sample temperature, pH, total microbial counts and total coliform (p<0.01). Legionella pneumophila was the most frequently isolated species (98.9%), and the isolated serogroups included serogroups 3 (25.3%), 6 (23.4%), 5 (19.2%), 1 (18.5%), 2 (10.2%), 8 (0.4%), 10 (0.8%), 9 (1.9%) and 12 (0.4%). Two hundred and twenty-eight isolates were analyzed by PFGE and 62 different patterns were obtained. Fifty-seven L. pneumophila isolates were selected for SBT analysis and divided into 35 different sequence types with 5 main clonal groups. All the 57 isolates had high intracellular growth ability.
  
  
  CONCLUSIONS
  Our results demonstrated high prevalence and genetic polymorphism of Legionella in springs in Beijing, China, and the SBT and intracellular growth assay results suggested that the Legionella isolates of hot spring environments were pathogenic. Improved control and prevention strategies are urgently needed.
authors.affiliation: State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Changping, Beijing, China. qintian@icdc.cn
authors.forename: Tian
authors.initials: T
authors.lastname: Qin
authors.forename: Gebin
authors.initials: G
authors.lastname: Yan
authors.forename: Hongyu
authors.initials: H
authors.lastname: Ren
authors.forename: Haijian
authors.initials: H
authors.lastname: Zhou
authors.forename: Huanxin
authors.initials: H
authors.lastname: Wang
authors.forename: Ying
authors.initials: Y
authors.lastname: Xu
authors.forename: Mingqiang
authors.initials: M
authors.lastname: Zhao
authors.forename: Hong
authors.initials: H
authors.lastname: Guan
authors.forename: Machao
authors.initials: M
authors.lastname: Li
authors.forename: Zhujun
authors.initials: Z
authors.lastname: Shao
mesh_terms: D002681:China; D016000:Cluster Analysis; D016521:Electrophoresis, Gel, Pulsed-Field; D014644:Genetic Variation; D045482:Hot Springs / Q000382:microbiology*; D007875:Legionella / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification; D062486:Public Health Surveillance; D011998:Recreation; D012621:Seasons; D014871:Water Microbiology; D060753:Water Quality