title: Amoxicillin resistance in Helicobacter pylori: studies from Tokyo, Japan from 1985 to 2003.
abstract: BACKGROUND
  Previous reports revealed no resistant strains of amoxicillin (AMPC), which is usually used in eradication therapy for H. pylori infection. However, the frequency and evolution of natural AMPC-resistant strains in the Japanese population remains unknown.
  
  
  OBJECTIVE
  To assess the prevalence of H. pylori resistance against AMPC in the Tokyo area, a collection of 648 H. pylori strains isolated from patients with GI diseases from 1985 to 2003 was tested for their sensitivity to AMPC.
  
  
  METHODS
  The susceptibility of the strains was assessed by determination of the minimal inhibitory concentration (MIC) using the E-test and/or the Dry-plate method. The susceptibility breakpoints of AMPC for H. pylori were: sensitive (AMPC-S); MIC < 0.04 microg/ml, intermittent resistance (AMPC-I); 0.04-1, resistant (AMPC-R); > 1.
  
  
  RESULTS
  No AMPC-R strains were detected in the strains isolated between 1985 and 1996, while the rate of resistance was determined to be 1.1%, 2.1%, 5.4%, 5.6%, 0%, 8.8%, and 1.5% every year, respectively, from 1997 to 2003. The percentage of AMPC-I strains increased from 2000 to 2003. The total eradication rate of H. pylori in the patients who received triple therapy containing AMPC was 81.4% (214/263). Classified as above, the rates of AMPC-S, AMPC-I, and AMPC-R were 84.6%, 77.8%, 25%, respectively.
  
  
  CONCLUSIONS
  H. pylori resistance to AMPC is still rare in Japan, although the percentage of AMPC-I strains has increased over the last 4 years. The frequency of isolation of strains showing true resistance to AMPC may increase in the future, along with an increase in the frequency of isolation of AMPC-I strains.
authors.affiliation: Third Department of Internal Medicine, Kyorin University School of Medicine, 6-20-2 Shinkawa, Mitaka, Tokyo 181-8611, Japan. kazjpgast@nifty.com
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Watanabe
authors.forename: Akifumi
authors.initials: A
authors.lastname: Tanaka
authors.forename: Kyoto
authors.initials: K
authors.lastname: Imase
authors.forename: Kengo
authors.initials: K
authors.lastname: Tokunaga
authors.forename: Hajime
authors.initials: H
authors.lastname: Sugano
authors.forename: Akemi
authors.initials: A
authors.lastname: Kai
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Ishida
authors.forename: Takeshi
authors.initials: T
authors.lastname: Itoh
authors.forename: Shin'ichi
authors.initials: S
authors.lastname: Takahashi
mesh_terms: D053799:2-Pyridinylmethylsulfinylbenzimidazoles; D000328:Adult; D000368:Aged; D000658:Amoxicillin / Q000494:pharmacology* / Q000627:therapeutic use; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001562:Benzimidazoles / Q000627:therapeutic use; D017291:Clarithromycin / Q000627:therapeutic use; D024881:Drug Resistance, Bacterial; D005260:Female; D016481:Helicobacter Infections / Q000188:drug therapy / Q000382:microbiology*; D016480:Helicobacter pylori / Q000187:drug effects* / Q000302:isolation & purification; D006801:Humans; D007564:Japan; D064747:Lansoprazole; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D009853:Omeprazole / Q000031:analogs & derivatives* / Q000627:therapeutic use; D064750:Rabeprazole; D014041:Tokyo
chemical_list: D053799:2-Pyridinylmethylsulfinylbenzimidazoles; D000900:Anti-Bacterial Agents; D001562:Benzimidazoles; D064747:Lansoprazole; D064750:Rabeprazole; D000658:Amoxicillin; D017291:Clarithromycin; D009853:Omeprazole