title: Studies on the development and stability of resistance of Helicobacter pylori to metronidazole and clarithromycin.
abstract: Thirty-one strains of Helicobacter pylori, susceptible to metronidazole and clarithromycin, were isolated from 31 biopsy samples from patients with various gastric pathologies. We investigated the possibility of selecting resistant strains and the stability of resistance by exposing isolates to increasing subinhibitory concentrations of metronidazole and clarithromycin using a serial passages technique. Resistance to metronidazole was obtained in 100% of the isolates, while 32.2% displayed resistance to clarithromycin. Resistance to metronidazole was stable in 93.5% (29 of 31) of the isolates, whereas 100% (10 of 10) of the strains were stably resistant to clarithromycin. The stability of the resistance that occurred after three passages on medium containing the two drugs was statistically significant (P <0.001). Thus, the technique of serial passages in vitro could be useful as a first screening in selecting drugs for use in therapeutic protocols for clinical trials.
authors.affiliation: Institute of Toxicological, Hygienic and Environmental Science, University of Urbino, Italy. baffone@uniurb.it
authors.forename: W
authors.initials: W
authors.lastname: Baffone
authors.forename: A
authors.initials: A
authors.lastname: Pianetti
authors.forename: B
authors.initials: B
authors.lastname: Citterio
authors.forename: G
authors.initials: G
authors.lastname: Lombardelli
authors.forename: E
authors.initials: E
authors.lastname: Vittoria
authors.forename: F
authors.initials: F
authors.lastname: Bruscolini
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D018929:Cell Culture Techniques; D017291:Clarithromycin / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004352:Drug Resistance, Microbial; D016481:Helicobacter Infections / Q000188:drug therapy; D016480:Helicobacter pylori / Q000187:drug effects* / Q000472:pathogenicity; D006801:Humans; D008795:Metronidazole / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests
chemical_list: D000900:Anti-Bacterial Agents; D008795:Metronidazole; D017291:Clarithromycin