title: Resistance of Helicobacter pylori strains to antibiotics in Korea with a focus on fluoroquinolone resistance.
abstract: OBJECTIVE
  New regimens, including those with new fluoroquinolones, have been developed to overcome the antibiotic resistance of Helicobacter pylori. We aimed to assess the antibiotic resistance rates, as well as the molecular mechanisms of fluoroquinolone resistance, of the clinical isolates obtained in Korea.
  
  
  METHODS
  The minimal inhibitory concentration (MIC) values of ciprofloxacin, amoxicillin, clarithromycin, metronidazole and tetracycline were determined by the agar dilution method for 185 treatment-naïve Helicobacter pylori isolates. The resistant strains were evaluated for the presence of point mutations in the quinolone resistance-determining region (QRDR) of the gyrA and gyrB genes by direct nucleotide sequencing.
  
  
  RESULTS
  Twenty-nine (29/185, 15.7%) of the strains were found to be resistant to ciprofloxacin. The resistance rates to amoxicillin, clarithromycin, metronidazole and tetracycline were 2.2% (four of 185), 10.8% (20 of 185), 30.3% (56 of 185) and 0.5% (one of 185), respectively. The most common mutations in the H. pylori gyrA gene were found at codons corresponding to Asp87 (16/29, 55.2%) and Asn91 (10/29, 34.5%).
  
  
  CONCLUSIONS
  Primary H. pylori resistance to ciprofloxacin occurred at a high frequency. The fluoroquinolone resistance is most likely mediated through amino acid point mutation in the gyrA gene at Asn87 and Asp91.
authors.affiliation: Department of Internal Medicine, Gachon Graduate School of Medicine, Gil Medical Center, Incheon, Korea.
authors.forename: Jun-Won
authors.initials: JW
authors.lastname: Chung
authors.forename: Gin Hyug
authors.initials: GH
authors.lastname: Lee
authors.forename: Jin-Yong
authors.initials: JY
authors.lastname: Jeong
authors.forename: Sun Mi
authors.initials: SM
authors.lastname: Lee
authors.forename: Ji Hoon
authors.initials: JH
authors.lastname: Jung
authors.forename: Kee Don
authors.initials: KD
authors.lastname: Choi
authors.forename: Ho June
authors.initials: HJ
authors.lastname: Song
authors.forename: Hwoon-Yong
authors.initials: HY
authors.lastname: Jung
authors.forename: Jin-Ho
authors.initials: JH
authors.lastname: Kim
mesh_terms: D000328:Adult; D000368:Aged; D000658:Amoxicillin / Q000494:pharmacology; D000668:Ampicillin Resistance; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002939:Ciprofloxacin / Q000494:pharmacology; D017291:Clarithromycin / Q000494:pharmacology; D027081:DNA Gyrase / Q000235:genetics*; D024881:Drug Resistance, Bacterial / Q000235:genetics; D024841:Fluoroquinolones / Q000494:pharmacology*; D016481:Helicobacter Infections / Q000188:drug therapy / Q000382:microbiology; D016480:Helicobacter pylori / Q000187:drug effects* / Q000235:genetics*; D006801:Humans; D008795:Metronidazole / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D017354:Point Mutation; D056910:Republic of Korea; D013752:Tetracycline / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D024841:Fluoroquinolones; D008795:Metronidazole; D002939:Ciprofloxacin; D000658:Amoxicillin; D027081:DNA Gyrase; D013752:Tetracycline; D017291:Clarithromycin