title: Contribution of efflux pumps to clarithromycin resistance in Helicobacter pylori.
abstract: OBJECTIVE
  Although clarithromycin (CLR) is one of the most commonly recommended component drugs of Helicobacter pylori eradication regimens, the prevalence of CLR-resistant H. pylori has been increasing. It is well known that CLR resistance is associated with point mutations in 23S rRNA, but an active multidrug efflux mechanism of H. pylori may also play a role in its drug resistance. At least four gene clusters have been identified as efflux pump systems in H. pylori and the present study was designed to investigate their role in the CLR resistance of clinical isolates of H. pylori.
  
  
  METHODS
  Fifteen CLR-resistant H. pylori strains (minimal inhibitory concentration [MIC]>or= 1 microg/mL) isolated from patients at Keio University Hospital were examined for expression of efflux pump mRNA by real-time polymerase chain reaction. In addition, the MIC of CLR in the presence or absence of Phe-Arg-beta-naphthylamide (PAbetaN), an efflux pump inhibitor (EPI), were determined.
  
  
  RESULTS
  In all 15 strains, efflux pump mRNA was expressed, and the MIC of CLR were decreased by using EPI, despite possessing 23s rRNA point mutations. In addition, the MIC of CLR was decreased by the EPI in a concentration-dependent fashion.
  
  
  CONCLUSIONS
  The efflux pump of H. pylori is associated with the development of resistance to CLR, in addition to 23S rRNA point mutations. Efflux pumps could be a novel target for reversing drug resistance in H. pylori.
authors.affiliation: Division of Gastroenterology and Hepatology, Department of Internal Medicine, Keio University School of Medicine, Tokyo, Japan.
authors.forename: Kenro
authors.initials: K
authors.lastname: Hirata
authors.forename: Hidekazu
authors.initials: H
authors.lastname: Suzuki
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Nishizawa
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Tsugawa
authors.forename: Hiroe
authors.initials: H
authors.lastname: Muraoka
authors.forename: Yoshimasa
authors.initials: Y
authors.lastname: Saito
authors.forename: Juntaro
authors.initials: J
authors.lastname: Matsuzaki
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Hibi
mesh_terms: D000368:Aged; D001426:Bacterial Proteins / Q000737:chemistry / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D017291:Clarithromycin / Q000378:metabolism / Q000494:pharmacology*; D004275:DNA, Ribosomal / Q000032:analysis; D004151:Dipeptides / Q000494:pharmacology; D024881:Drug Resistance, Bacterial; D005260:Female; D020459:Genes, rRNA; D016481:Helicobacter Infections / Q000188:drug therapy* / Q000382:microbiology; D016480:Helicobacter pylori / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D006801:Humans; D008297:Male; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D008958:Models, Molecular; D017354:Point Mutation; D011487:Protein Conformation; D012329:RNA, Bacterial; D012338:RNA, Ribosomal, 23S
chemical_list: D001426:Bacterial Proteins; D004275:DNA, Ribosomal; D004151:Dipeptides; D026901:Membrane Transport Proteins; D012329:RNA, Bacterial; D012338:RNA, Ribosomal, 23S; C419365:phenylalanine arginine beta-naphthylamide; D017291:Clarithromycin