title: Prevalence of fluoroquinolone-resistant Escherichia coli O25:H4-ST131 (CTX-M-15-nonproducing) strains isolated in Japan.
abstract: BACKGROUND
  Fluoroquinolone-resistant and extended-spectrum β-lactamase (ESBL)-carrying multidrug-resistant Escherichia coli have become severely problematic. In particular, a lineage of multilocus sequence-type ST131 which belongs to O25:H4 and carries ESBL CTX-M-15 has spread worldwide.
  
  
  METHODS
  Fluoroquinolone-resistant E. coli strains were isolated from various clinical specimens in a commercial clinical laboratory in 2008 and 2009 in Hokkaido Prefecture, Japan.
  
  
  RESULTS
  Among 478 clinical isolates, 112 strains (23.4%) showed levofloxacin (LVX) resistance. About 80% of the fluoroquinolone-resistant strains (88 strains) showed common features, namely O25:H4-ST131, phylogenetic group B and the same mutation pattern in quinolone resistance-determining regions. Pulsed field gel electrophoresis patterns suggested numerous lineages of O25:H4-ST131. The fluoroquinolone-resistant strains, including strains of O25:H4-ST131 and other types, more frequently shared CTX-type ESBL genes than did fluoroquinolone-susceptible strains. The ESBL genes fell into the CTX-M-9 and CTX-M-2 groups. CTX-M-15 (CTX-M-1 group) was not found among any of the strains isolated in this study. Sitafloxacin showed markedly potent activity against E. coli isolates compared with LVX, ciprofloxacin and ulifloxacin.
  
  
  CONCLUSIONS
  The most prevalent fluoroquinolone-resistant strains of E. coli isolated in Hokkaido Prefecture, Japan, are O25:H4-ST131. However, similar to other areas of Japan, the ST131 clones represent distinct lineages from the general worldwide dispersal of multidrug-resistant clones which carry CTX-M-15.
authors.affiliation: Department of Microbiology, Sapporo Medical University School of Medicine, Sapporo, Japan.
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Yokota
authors.forename: Toyotaka
authors.initials: T
authors.lastname: Sato
authors.forename: Torahiko
authors.initials: T
authors.lastname: Okubo
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Ohkoshi
authors.forename: Tamaki
authors.initials: T
authors.lastname: Okabayashi
authors.forename: Osamu
authors.initials: O
authors.lastname: Kuwahara
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Tamura
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Fujii
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002648:Child; D002675:Child, Preschool; D027081:DNA Gyrase / Q000235:genetics; D027101:DNA Topoisomerase IV / Q000235:genetics; D004269:DNA, Bacterial / Q000032:analysis / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field; D004926:Escherichia coli / Q000145:classification / Q000187:drug effects* / Q000302:isolation & purification / Q000502:physiology*; D004927:Escherichia coli Infections / Q000453:epidemiology / Q000382:microbiology*; D029968:Escherichia coli Proteins / Q000235:genetics; D005260:Female; D024841:Fluoroquinolones / Q000494:pharmacology*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007564:Japan; D064704:Levofloxacin; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D015242:Ofloxacin / Q000494:pharmacology; D015995:Prevalence; D055815:Young Adult; D001618:beta-Lactamases / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D024841:Fluoroquinolones; D064704:Levofloxacin; D015242:Ofloxacin; C473109:beta-lactamase CTX-M-15; D001618:beta-Lactamases; D027101:DNA Topoisomerase IV; D027081:DNA Gyrase