title: Association of metronidazole resistance and natural competence in Helicobacter pylori.
abstract: To study whether the capability of horizontal DNA transfer is associated with metronidazole resistance in Helicobacter pylori, a total of 81 clinical isolates were tested for MICs of metronidazole (MTZ). The MIC assays were performed by using the E-test and reconfirmed by the agar dilution method. Natural competence assays were performed by transferring a chloramphenicol acetyltransferase cassette and a 23S rRNA gene from a clarithromycin-resistant strain (with an A-to-G mutation at nucleotide 2143) by using natural transformation. Of the 81 isolates, 65 (80.2%) were naturally competent while 16 were not. Among the 65 naturally competent strains, 39 (60%) were highly resistant to MTZ (MICs, >32 microg/ml) while only 2 of 16 (12.5%) noncompetent strains were highly MTZ resistant (P, <0.001). Therefore, there is an association between natural competence and MTZ resistance.
authors.affiliation: Graduate Institute of Microbiology, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Yu-Ching
authors.initials: YC
authors.lastname: Yeh
authors.forename: Kai-Chin
authors.initials: KC
authors.lastname: Chang
authors.forename: Jyh-Chin
authors.initials: JC
authors.lastname: Yang
authors.forename: Chi-Tai
authors.initials: CT
authors.lastname: Fang
authors.forename: Jin-Town
authors.initials: JT
authors.lastname: Wang
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics; D024881:Drug Resistance, Bacterial; D016481:Helicobacter Infections / Q000382:microbiology; D016480:Helicobacter pylori / Q000187:drug effects* / Q000235:genetics*; D006801:Humans; D008795:Metronidazole / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D012338:RNA, Ribosomal, 23S / Q000235:genetics; D014169:Transformation, Bacterial
chemical_list: D000900:Anti-Bacterial Agents; D012338:RNA, Ribosomal, 23S; D008795:Metronidazole; D015500:Chloramphenicol O-Acetyltransferase