title: Change in the prevalence of extended-spectrum-beta-lactamase-producing Escherichia coli in Japan by clonal spread.
abstract: BACKGROUND
  In the early 2000s, there was a rapid increase in extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli in hospital settings throughout Japan. The reasons for this rapid increase are unclear.
  
  
  METHODS
  Between 2002 and 2003, 142 clinical isolates of E. coli suspected of producing ESBL were obtained from 37 hospitals and commercial clinical laboratories in geographically distinct regions throughout Japan. They were tested for ESBL types and further subtyped for serogroups, fimH single nucleotide polymorphism, pulsed-field gel electrophoresis patterns and multilocus sequence type (MLST). Representative isolates were also subjected to plasmid analysis.
  
  
  RESULTS
  Of 142 E. coli isolates suspected of producing ESBL, 130 were confirmed as harbouring blaCTX-M by PCR analysis and sequencing. Of these, 84 (65%) harboured CTX-M-9-group blaCTX-M. Two serogroups O25 and O86 accounted for 41% of the 130 blaCTX-M-positive E. coli. All O86 serogroup strains belonged to ST38 by MLST and they formed 18% of all the blaCTX-M-positive E. coli. Serogroup O25 strains belonged to ST131 and ST73, and formed 21% and 1% of blaCTX-M-positive E. coli, respectively. Seven characterized plasmids carrying blaCTX-M genes belonged to three distinct incompatibility groups: IncF, IncN and IncI1.
  
  
  CONCLUSIONS
  In this study, clonally related strains of E. coli accounted for a large proportion of blaCTX-M-positive E. coli. This high proportion of clonal groups identified in different regions of Japan suggests their recent spread by mechanisms other than healthcare-associated transmission. These observations imply that restricting antimicrobial use in human clinical settings may have limited impact on the spread of ESBL-producing E. coli.
authors.affiliation: Department of Bacterial Pathogenesis and Infection Control, National Institute of Infectious Diseases, 4-7-1 Musashi-murayama, Tokyo 208-0011, Japan.suzukiss@nih.go.jp
authors.forename: Satowa
authors.initials: S
authors.lastname: Suzuki
authors.forename: Naohiro
authors.initials: N
authors.lastname: Shibata
authors.forename: Kunikazu
authors.initials: K
authors.lastname: Yamane
authors.forename: Jun-ichi
authors.initials: J
authors.lastname: Wachino
authors.forename: Kenitiro
authors.initials: K
authors.lastname: Ito
authors.forename: Yoshichika
authors.initials: Y
authors.lastname: Arakawa
mesh_terms: D015373:Bacterial Typing Techniques; D016000:Cluster Analysis; D016172:DNA Fingerprinting; D004926:Escherichia coli / Q000145:classification / Q000187:drug effects* / Q000201:enzymology* / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000453:epidemiology* / Q000382:microbiology*; D005798:Genes, Bacterial; D005838:Genotype; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008826:Microbial Sensitivity Tests; D017720:Molecular Epidemiology; D010957:Plasmids / Q000145:classification; D016133:Polymerase Chain Reaction; D015995:Prevalence; D017422:Sequence Analysis, DNA; D012703:Serotyping; D001618:beta-Lactamases / Q000096:biosynthesis / Q000235:genetics*
chemical_list: D001618:beta-Lactamases