title: Mutations of Helicobacter pylori associated with fluoroquinolone resistance in Korea.
abstract: OBJECTIVE
  Fluoroquinolone resistance of Helicobacter pylori is known to be dependent on mutations in the QRDR of gyrA. This study was performed to investigate the distribution of gyrA point mutations and to evaluate the impact of the mutations on second-line H. pylori eradication therapy.
  
  
  METHODS
  After H. pylori isolation from gastric mucosal specimens, fluoroquinolone resistance was examined using the agar dilution method. DNA sequencing of the QRDR of gyrA was performed in 89 fluoroquinolone-resistant and 27 fluoroquinolone-susceptible isolates. Transformation experiments were performed to confirm mutations in the resistant strains. The eradication rates of moxifloxacin-containing triple therapy were evaluated depending on the resistance of fluoroquinolone.
  
  
  RESULTS
  The gyrA mutations were detected in 75.3% (55 of 73 strains) of the primary resistant strains and 100% (16 strains) of the secondary resistant strains. The most common mutations were Asp-91 (36.0%) and Asn-87 (33.7%). The MIC values in the transformed strains differed depending on the gyrA mutations, N87, and D91. Six patients with fluoroquinolone-resistant strains received moxifloxacin-containing triple therapy as the second-line therapy, and two of three patients with Asn-87 mutations (66.7%) failed in the eradication. By contrast, three patients with Asp-91 mutations had successful eradication treatment.
  
  
  CONCLUSIONS
  Fluoroquinolone resistance of H. pylori was caused by gyrA Asn-87 and Asp-91 point mutations. The Asn-87 mutation seems to be an important determinant of failure of fluoroquinolone-containing triple eradication therapy based on eradication results.
authors.affiliation: Department of Internal Medicine, Seoul National University Bundang Hospital, Seongnam, Gyeonggi-do, Korea.
authors.forename: Jung W
authors.initials: JW
authors.lastname: Lee
authors.forename: Nayoung
authors.initials: N
authors.lastname: Kim
authors.forename: Ryoung H
authors.initials: RH
authors.lastname: Nam
authors.forename: Ji H
authors.initials: JH
authors.lastname: Park
authors.forename: Jung M
authors.initials: JM
authors.lastname: Kim
authors.forename: Hyun C
authors.initials: HC
authors.lastname: Jung
authors.forename: In S
authors.initials: IS
authors.lastname: Song
mesh_terms: D000368:Aged; D000900:Anti-Bacterial Agents / Q000494:pharmacology* / Q000627:therapeutic use; D027081:DNA Gyrase / Q000235:genetics*; D024881:Drug Resistance, Bacterial; D005260:Female; D024841:Fluoroquinolones / Q000494:pharmacology* / Q000627:therapeutic use; D016481:Helicobacter Infections / Q000188:drug therapy / Q000382:microbiology*; D016480:Helicobacter pylori / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D006801:Humans; D007723:Korea; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D020125:Mutation, Missense; D017422:Sequence Analysis, DNA; D017211:Treatment Failure
chemical_list: D000900:Anti-Bacterial Agents; D024841:Fluoroquinolones; D027081:DNA Gyrase