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

Background: Therapy for Helicobacter pylori is generally empiric despite th e fact that resistance to metronidazole and clarithromycin compromise thera peutic 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 resistan ce among H pylori isolated from patients enrolled in US-based clinical tria ls between 1993 and 1999 was reviewed in relation to patient age, sex, regi on of the United States, and test method (Etest and 2 agar dilution procedu res). Results: Clarithromycin and metronidazole resistance rates were based on th e results of 3439 pretreatment Etest determinations and 3193 agar dilution determinations. Sex and age were available on 900 and 823 individuals, resp ectively. Metronidazole resistance was 39% by Etest and 21.6% by agar dilut ion (P<.001). Clarithromycin re resistance was 12% by Etest and 10.6% by ag ar 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. Re gional 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 t o metronidazole and clarithromycin may soon require the performance of anti microbial susceptibility testing of H pylori isolates prior to initiating t reatment.