Clarithromycin-resistant Helicobacter pylori in patients with duodenal ulcer in the United States.

Abstract

Clarithromycin is a key component of several antimicrobial treatment regimens for Helicobacter pylori. Cure rates with clarithromycin-containing regimens are significantly decreased when resistance is present. Resistance develops by a point mutation in the ribosomal RNA of some organisms exposed to clarithromycin. We studied the prevalence of clarithromycin-resistant organisms in patients with duodenal ulcer in the United States from 1993-96. Patients with endoscopic evidence of a duodenal ulcer were studied. Gastric biopsies were cultured for H. pylori and antimicrobial sensitivity was determined by the E-test (epsilometer agar diffusion gradient). In 1993-94, three of 78 patients (4%) had clarithromycin-resistant strains of H. pylori. In 1995-96, 44 of 348 patients (12.6%; p = 0.025) had resistant strains of H. pylori. Patients who had previously failed antimicrobial treatment for H. pylori accounted for much of the increase in resistant strains (25%). Failed therapy with clarithromycin-based regimens is a growing cause of antimicrobial resistance in H. pylori in the United States. Whereas the overall rates of primary resistance are low, the increase in secondary resistance over a short period of time is worrisome. New treatments that prevent the emergence of resistance may be important in the future.