Pattern of primary resistance of Helicobacter pylori to metronidazole or clarithromycin in the United States

Background: Therapy for Helicobacter pylori is generally empiric despite the fact that resistance to metronidazole and clarithromycin compromise therapeutic efficacy. The aim of this study was to aid clinicians in choosing a course of therapy for H pylori infection in the United States. Methods: The frequency of primary clarithromycin and metronidazole resistance among H pylori isolated from patients enrolled in US-based clinical trials between 1993 and 1999 was reviewed in relation to patient age, sex, region of the United States, and test method (Etest and 2 agar dilution procedures). Results: Clarithromycin and metronidazole resistance rates were based on the results of 3439 pretreatment Etest determinations and 3193 agar dilution determinations. Sex and age were available on 900 and 823 individuals, respectively. Metronidazole resistance was 39% by Etest and 21.6% by agar dilution (P<.001). Clarithromycin re resistance was 12% by Etest and 10.6% by agar dilution. Amoxicillin or tetracycline resistance was rare. Metronidazole and clarithromycin resistance was more common in women than men leg, 34.7% vs 22.6% for metronidazole and 14.1% vs 9.7% for clarithromycin (P=.01 and P=.06, respectively). Antibiotic resistance increased gradually up to age 70 years, then declined significantly (P<.05) regardless of test method. Regional differences in antimicrobial resistance did not occur. Conclusions: While age and sex had significant effects on resistance rates, regional differences were not present. The high prevalence of resistance to metronidazole and clarithromycin may soon require the performance of antimicrobial susceptibility testing of H pylori isolates prior to initiating treatment.