title: Primary levofloxacin resistance and gyrA/B mutations among Helicobacter pylori in Japan.
abstract: BACKGROUND
  Recent years have witnessed a decrease in the rate of Helicobacter pylori eradication due to antimicrobial resistance, clarithromycin or metronidazole resistance in particular. As one of the alternatives to the standard regimens, levofloxacin-containing therapy has been considered a promising regimen. Nevertheless, there is a little information concerning the prevalence of levofloxacin resistance and this resistance mechanism.
  
  
  METHODS
  Levofloxacin susceptibility was examined using E-test in 507 H. pylori strains clinically isolated in Japan from 2001 to 2004. Mutation patterns in the quinolone resistance-determining regions of the gyrA and gyrB genes were evaluated, performing direct sequencing of 68 levofloxacin-resistant and 50 susceptible strains.
  
  
  RESULTS
  Primary levofloxacin resistance was found in 76 (15.0%) strains. Fifty-seven (83.8%) of 68 levofloxacin-resistant strains analyzed had point mutations in gyrA at Asn-87 or Asp-91, while seven (14.0%) of 50 susceptible strains had gyrA mutations. There was a significant difference in the occurrence of gyrA mutations between levofloxacin-resistant and -susceptible strains (p < .001). In levofloxacin-resistant strains, the occurrence of gyrA mutations at Asn-87 was most common regardless of minimal inhibitory concentration levels, and that of gyrA mutations at Asp-91 tended to be associated with low-level resistance. A double gyrA mutation at Asn-87 and Asp-91 might have an additional impact. As for gyrB, three (4.4%) of 68 levofloxacin-resistant strains with no susceptible strains had mutations.
  
  
  CONCLUSIONS
  Primary levofloxacin resistance was common in Japan and primarily related to gyrA mutations at Asn-87 and Asp-91.
authors.affiliation: Division of Diabetes, Digestive and Kidney Diseases, Department of Clinical Molecular Medicine, Kobe University Graduate School of Medicine, Kobe, Japan.
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Miyachi
authors.forename: Ikuya
authors.initials: I
authors.lastname: Miki
authors.forename: Nobuo
authors.initials: N
authors.lastname: Aoyama
authors.forename: Daisuke
authors.initials: D
authors.lastname: Shirasaka
authors.forename: Yuko
authors.initials: Y
authors.lastname: Matsumoto
authors.forename: Masanori
authors.initials: M
authors.lastname: Toyoda
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Mitani
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Morita
authors.forename: Takao
authors.initials: T
authors.lastname: Tamura
authors.forename: Shohiro
authors.initials: S
authors.lastname: Kinoshita
authors.forename: Yoshie
authors.initials: Y
authors.lastname: Okano
authors.forename: Shunichi
authors.initials: S
authors.lastname: Kumagai
authors.forename: Masato
authors.initials: M
authors.lastname: Kasuga
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000235:genetics; D027081:DNA Gyrase / Q000235:genetics*; D004252:DNA Mutational Analysis; D004269:DNA, Bacterial / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D005260:Female; D016481:Helicobacter Infections / Q000382:microbiology*; D016480:Helicobacter pylori / Q000187:drug effects* / Q000201:enzymology; D006801:Humans; D007564:Japan; D064704:Levofloxacin; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D009154:Mutation; D015242:Ofloxacin / Q000494:pharmacology*; D017422:Sequence Analysis, DNA
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D064704:Levofloxacin; D015242:Ofloxacin; D027081:DNA Gyrase