title: Emergence and spread of O16-ST131 and O25b-ST131 clones among faecal CTX-M-producing Escherichia coli in healthy individuals in Hunan Province, China.
abstract: OBJECTIVE
  The objectives of this study were to determine CTX-M-producing Escherichia coli ST131 strain prevalence in stool specimens from healthy subjects in central China and to molecularly characterize clonal groups.
  
  
  METHODS
  From November 2013 to January 2014, stool specimens from healthy individuals in Hunan Province were screened for ESBL-producing E. coli using chromogenic medium and CTX-M genotypes and phylogenetic groups were determined. ST131 clonal groups were detected by PCR and characterized for antibiotic resistance, fimH, gyrA and parC alleles, plasmid-mediated quinolone resistance determinants, virulence genotypes and PFGE patterns.
  
  
  RESULTS
  Among 563 subjects, 287 (51.0%) exhibited the presence of faecal ESBL-producing E. coli, all of which produced CTX-M enzymes. The most common CTX-M genotypes were CTX-M-14 (48.4%), CTX-M-15 (27.5%) and CTX-M-27 (15.0%). Of the 287 CTX-M-producing isolates, 32 (11.1%) belonged to the ST131 clone. O16-ST131 isolates were dominant (75%) and contained the fimH41 allele. The remaining eight (25%) ST131 isolates were of the O25b subgroup and contained fimH30 or fimH41. Ciprofloxacin resistance was found in 100% of the O25b-ST131 isolates, whereas only 8% of the O16-ST131 isolates were resistant. All of the O25b-ST131 isolates except one showed gyrA1AB and parC1aAB mutations; most of the O16-ST131 isolates had gyrA1A and parC1b mutations. The virulence genotypes of O16-ST131 resembled those of the O25b-ST131 isolates. The 32 ST131 isolates formed one large group at the 64% similarity level. They comprised 15 PFGE groups (defined at ≥85% similarity).
  
  
  CONCLUSIONS
  O16-ST131 isolates have emerged as the predominant type of ST131 isolate in faecal CTX-M-producing E. coli in healthy individuals in China.
authors.affiliation: Department of Clinical Laboratory, Xiangya Hospital, Central South University, Changsha 410008, Hunan Province, China.
authors.forename: Yi-Ming
authors.initials: YM
authors.lastname: Zhong
authors.affiliation: Department of Clinical Laboratory, Xiangya Hospital, Central South University, Changsha 410008, Hunan Province, China wenenliu@163.com.
authors.forename: Wen-En
authors.initials: WE
authors.lastname: Liu
authors.affiliation: Department of Clinical Laboratory, Xiangya Hospital, Central South University, Changsha 410008, Hunan Province, China.
authors.forename: Xiang-Hui
authors.initials: XH
authors.lastname: Liang
authors.affiliation: Department of Clinical Laboratory, Xiangya Hospital, Central South University, Changsha 410008, Hunan Province, China.
authors.forename: Yan-Ming
authors.initials: YM
authors.lastname: Li
authors.affiliation: Department of Clinical Laboratory, Xiangya Hospital, Central South University, Changsha 410008, Hunan Province, China.
authors.forename: Zi-Juan
authors.initials: ZJ
authors.lastname: Jian
authors.affiliation: PHE Public Health Laboratory Birmingham, Heart of England NHS Foundation Trust, Birmingham B9 5SS, UK Institute of Microbiology and Infection, University of Birmingham, Birmingham B15 2TT, UK.
authors.forename: Peter M
authors.initials: PM
authors.lastname: Hawkey
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002681:China / Q000453:epidemiology; D003430:Cross-Sectional Studies; D052978:Disk Diffusion Antimicrobial Tests; D016521:Electrophoresis, Gel, Pulsed-Field; D004926:Escherichia coli / Q000145:classification* / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000453:epidemiology* / Q000382:microbiology*; D005243:Feces / Q000382:microbiology*; D005260:Female; D005838:Genotype; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D008875:Middle Aged; D017720:Molecular Epidemiology; D058889:Molecular Typing; D010802:Phylogeny; D010957:Plasmids / Q000032:analysis; D037521:Virulence Factors / Q000235:genetics; D055815:Young Adult; D001618:beta-Lactamases / Q000235:genetics*
chemical_list: D037521:Virulence Factors; D001618:beta-Lactamases
keywords: E. coli; ESBLs; faecal carriage; genotypes