Antibiotic susceptibilities of Helicobacter pylori strains isolated in the Province of Alberta.

The incidence of antibiotic resistance to amoxicillin, clarithromycin, erythromycin, metronidazole and tetracycline in Helicobacter pylori strains isolated from gastric biopsy specimens obtained in Alberta was investigated. Results for all antibiotics were obtained using agar dilution, and in addition to metronidazole, the E test was used. Resistance to amoxicillin and tetracycline was not detected. Metronidazole resistance determined using agar dilution was approximately 12% (95% CI 4% to 26%) when minimal inhibitory concentrations (MICs) were at least 8 micrograms/mL, but fell to 2% (95% CI 0.1% to 13%) when MICs were set at 32 micrograms/mL or greater. The E test for metronidazole resistance (MIC 8 micrograms/mL or greater) yielded a slightly higher percentage of resistant strains compared with agar dilution tests (14%, 95% CI 5% to 29%). One of the 31 strains was resistant to clarithromycin (MIC 8 micrograms/mL) and erythromycin (MIC 16 micrograms/mL). Thus, the incidence of resistance to clarithromycin, part of the currently used triple therapy for eradication of H pylori, was 3% (95% CI 0.1% to 17%).