title: Levofloxacin-resistant Helicobacter pylori in Hong Kong.
abstract: BACKGROUND
  Fluoroquinolone-resistant Helicobacter pylori emerged in 1995 and the resistance was due to point mutation in the gyrA gene. In this study we investigate the resistance mechanism and the antimicrobial susceptibilities of clarithromycin, metronidazole, amoxicillin, tetracycline and telithromycin against levofloxacin-resistant H. pylori in Hong Kong.
  
  
  METHODS
  One hundred and ninety-one nonduplicate H. pylori isolates were collected during 2004 and 2005, and 25 isolates with levofloxacin zone sizes less than 30 mm were selected for minimal inhibitory concentration determination by agar dilution, gyrA gene amplication and sequencing the amplified gyrA gene.
  
  
  RESULTS
  The prevalence of levofloxacin-resistant H. pylori was 11.5% (22/191). Among these levofloxacin-resistant strains, 7 (31.8%) and 10 (45.5%) were resistant to clarithromycin and metronidazole, respectively, 17 (77.3%) had point mutations in gyrA gene at amino acids 87, 91 and 130 and the most frequent mutation point was at position 91.
  
  
  CONCLUSIONS
  Amoxicillin, tetracycline and telithromycin were active against levofloxacin-resistant H. pylori and levofloxacin resistance was mainly due to point mutation in the gyrA gene, especially at amino acid position 91.
authors: Department of Microbiology, The Chinese University of Hong Kong, Prince of Wales Hospital, Hong Kong, SAR, China.
authors: Ching Ching
authors: CC
authors: Lee
authors: Vivian W Y
authors: VW
authors: Lee
authors: Francis K L
authors: FK
authors: Chan
authors: Thomas K W
authors: TK
authors: Ling
mesh_terms: D000658:Amoxicillin / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D017291:Clarithromycin / Q000494:pharmacology; D027081:DNA Gyrase / Q000235:genetics; D004252:DNA Mutational Analysis; D004269:DNA, Bacterial; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D016481:Helicobacter Infections / Q000382:microbiology; D016480:Helicobacter pylori / Q000187:drug effects* / Q000235:genetics; D006723:Hong Kong; D006801:Humans; D048628:Ketolides / Q000494:pharmacology; D064704:Levofloxacin; D008795:Metronidazole / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D015242:Ofloxacin / Q000494:pharmacology*; D017354:Point Mutation; D013752:Tetracycline / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D048628:Ketolides; D008795:Metronidazole; D064704:Levofloxacin; D000658:Amoxicillin; D015242:Ofloxacin; D027081:DNA Gyrase; D013752:Tetracycline; D017291:Clarithromycin; C106791:telithromycin