title: Nationwide high prevalence of CTX-M and an increase of CTX-M-55 in Escherichia coli isolated from patients with community-onset infections in Chinese county hospitals.
abstract: BACKGROUND
  In order to investigate the epidemiology, molecular characteristics, and distribution of extended-spectrum β-lactamase (ESBL)- and AmpC-producing Escherichia coli from community-onset infections in Chinese county hospitals.
  
  
  METHODS
  E. coli isolates were collected from patients with community-onset infections in 30 county hospitals. ESBL activity was confirmed by double-disc diffusion. Genetic confirmation and molecular typing of ESBL- and AmpC-producing isolates was determined by PCR and DNA sequencing. ESBL-positive isolates were further characterised by multi-locus sequence typing.
  
  
  RESULTS
  Of 550 E. coli isolates, 256 (46.5%) carried ESBL genes and all were of the CTX-M type. The prevalence of ESBL-producing strains varied from 30.2% to 57.0% across different regions of China. Overall, 12 bla CTX-M subtypes were detected; the most abundant were bla CTX-M-14 (163/256 isolates, 64.5%), bla CTX-M-55 (47/256, 18.4%), and bla CTX-M-15 (31/256, 12.1%). CMY-2-like AmpC β-lactamases were detected in 11 strains, three of which co-existed with bla CTX-M. A total of 64 sequence types (STs) were detected in 256 ESBL-producing strains, including nine that were new. ST131 was the most abundant type (27 isolates, 12.7%), followed by ST69 (14 isolates, 6.6%), ST405 (14 isolates, 6.6%), and ST38 (12 isolates, 5.6%).
  
  
  CONCLUSIONS
  This study revealed that the widespread prevalence of ESBLs among outpatient infections has reached a high level in county hospitals. The CTX-M genotype was most dominant, comprising a variety of subtypes. This is the first time the incidence of CTX-M-55 has exceeded that of CTX-M-15 in China. No predominant ST was detected, suggesting that ESBL-producing E. coli strains originate in different clones.
authors.affiliation: Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, State Key Laboratory for Diagnosis and Treatment of Infectious Disease, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, 310003, China. z-j2011@hotmail.com.
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, State Key Laboratory for Diagnosis and Treatment of Infectious Disease, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, 310003, China. mpio@163.com.
authors.forename: Beiwen
authors.initials: B
authors.lastname: Zheng
authors.affiliation: Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, State Key Laboratory for Diagnosis and Treatment of Infectious Disease, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, 310003, China. lnzhao@live.cn.
authors.forename: Lina
authors.initials: L
authors.lastname: Zhao
authors.affiliation: Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, State Key Laboratory for Diagnosis and Treatment of Infectious Disease, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, 310003, China. zeqingw@163.com.
authors.forename: Zeqing
authors.initials: Z
authors.lastname: Wei
authors.affiliation: Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, State Key Laboratory for Diagnosis and Treatment of Infectious Disease, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, 310003, China. susu0572@126.com.
authors.forename: Jinru
authors.initials: J
authors.lastname: Ji
authors.affiliation: Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, State Key Laboratory for Diagnosis and Treatment of Infectious Disease, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, 310003, China. ljli@zju.edu.cn.
authors.forename: Lanjuan
authors.initials: L
authors.lastname: Li
authors.affiliation: Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, State Key Laboratory for Diagnosis and Treatment of Infectious Disease, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, 310003, China. xiao-yonghong@163.com.
authors.forename: Yonghong
authors.initials: Y
authors.lastname: Xiao
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D015373:Bacterial Typing Techniques; D002681:China / Q000453:epidemiology; D017714:Community-Acquired Infections / Q000453:epidemiology / Q000382:microbiology; D004269:DNA, Bacterial / Q000032:analysis; D004926:Escherichia coli / Q000145:classification* / Q000201:enzymology / Q000235:genetics / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000382:microbiology*; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism; D005260:Female; D005819:Genetic Markers; D005838:Genotype; D006766:Hospitals, County; D006801:Humans; D008297:Male; D008875:Middle Aged; D058885:Multilocus Sequence Typing; D016133:Polymerase Chain Reaction; D015995:Prevalence; D017422:Sequence Analysis, DNA; D055815:Young Adult; D001618:beta-Lactamases / Q000235:genetics* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D005819:Genetic Markers; C048795:AmpC beta-lactamases; D001618:beta-Lactamases; C000602253:beta-lactamase CTX-M, E coli; C000602254:beta-lactamase CTX-M-55, E coli