title: Multilocus sequence typing indicates diverse origins of invasive Candida tropicalis isolates in China.
abstract: BACKGROUND
  According to data from the China Hospital Invasive Fungal Surveillance Net (CHIF-NET) 2010, Candida tropicalis (C. tropicalis) is the third most common pathogen causing invasive candidiasis. Moreover, the majority of fluconazole-resistant C. tropicalis isolates were from a single hospital. Therefore, a molecular epidemiological survey is necessary to investigate the genetic relatedness of C. tropicalis isolates in China.
  
  
  METHODS
  In this study, 48 C. tropicalis isolates causing invasive fungal infections from four tertiary hospitals in China were studied. All the isolates were identified by sequencing the internal transcribed spacer region. Antifungal susceptibility to triazoles, amphotericin B, and caspofungin was determined by the Clinical and Laboratory Standards Institute standard broth microdilution method. Multilocus sequence typing (MLST) was performed, and phylogenetic analysis was further performed by the eBURST and maximum parsimony (MP) methods to characterize the genetic relatedness of isolates.
  
  
  RESULTS
  MLST discriminated 40 diploid sequence types (DSTs) among 48 isolates, including 36 novel DSTs, and the XYR1 gene showed the highest discriminatory power. The DSTs obtained from this study were compared with those of previously reported C. tropicalis isolates, and there was poor type alignment with regional strains. Nine groups and 11 singletons were identified by eBURST, whereas two groups and 10 subgroups were clustered by MP analysis. Generally, there were no obvious correlations between clonal clusters generated and the specimen source or hospital origin. Seven fluconazole-resistant isolates were confirmed and assigned to three distinguishable branches.
  
  
  CONCLUSIONS
  The results suggested diverse origins of invasive C. tropicalis isolates in China. Although most invasive C. tropicalis strains in the mainland of China were clustered with previously characterized Asian isolates, major C. tropicalis clusters identified in this study were genetically distinct from those of other geographic regions.
authors.affiliation: Graduate School, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing 100730, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Fan
authors.affiliation: Department of Clinical Laboratory, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing 100730, China.
authors.forename: Meng
authors.initials: M
authors.lastname: Xiao
authors.affiliation: Department of Clinical Laboratory, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing 100730, China.
authors.forename: He
authors.initials: H
authors.lastname: Wang
authors.affiliation: Graduate School, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing 100730, China.
authors.forename: Li
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Centre for Infectious Diseases and Microbiology Laboratory Services, Westmead Hospital, Darcy Road, Westmead, New South Wales, Australia.
authors.forename: Fanrong
authors.initials: F
authors.lastname: Kong
authors.affiliation: Department of Clinical Laboratory, First Affiliated Hospital of Harbin Medical University, Harbin, Heilongjiang 150001, China.
authors.forename: Juan
authors.initials: J
authors.lastname: Lu
authors.affiliation: Department of Clinical Laboratory, Tianjin Medical University General Hospital, Tianjin 300052, China.
authors.forename: Zhidong
authors.initials: Z
authors.lastname: Hu
authors.affiliation: Laboratory of Clinical Microbiology, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China.
authors.forename: Mei
authors.initials: M
authors.lastname: Kang
authors.affiliation: Department of Clinical Laboratory, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing 100730, China. Email: xycpumch@139.com.
authors.forename: Yingchun
authors.initials: Y
authors.lastname: Xu
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000935:Antifungal Agents / Q000627:therapeutic use; D041022:Candida tropicalis / Q000187:drug effects / Q000472:pathogenicity*; D002177:Candidiasis / Q000188:drug therapy*; D002681:China; D025141:Drug Resistance, Fungal / Q000235:genetics; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D058885:Multilocus Sequence Typing / Q000379:methods*; D010802:Phylogeny; D055815:Young Adult
chemical_list: D000935:Antifungal Agents