Metronidazole-resistant Helicobacter pylori is more prevalent in patients with nonulcer dyspepsia than in peptic ulcer patients in a multiethnic Asian population.

The trend of increasing prevalence of antibiotic resistance among Helicobacter pylori strains has been suggested as a cause of the failure of treatment of H. pylori infections. In this study, 120 of 211 antral biopsy specimens from patients with dyspeptic symptoms were found to harbor H. pylori. The isolates from the 120 specimens were tested by the agar dilution method, and 38 (31.7%) were found to be metronidazole resistant. Among the 211 subjects, 81 of 115 (70.4%) patients with peptic ulcer (PU) were infected with H. pylori, whereas 39 of 96 (40.6%) patients with nonulcer dyspepsia (NUD) were infected with H. pylori. Interestingly, significantly more NUD patients than PU patients harbored metronidazole-resistant H. pylori (22 of 39 [56.4%] and 16 of 81 [19.8%], respectively; P < 0.001). A similar pattern was also observed among NUD patients of different ethnicities but not between male and female patients (23 of 78 [29.5%] and 15 of 42 [35.7%], respectively; P = 0.54). In the posttreatment follow-up, five of six patients who had positive urea breath test results, indicating treatment failure, were NUD patients. Of these, four harbored metronidazole-resistant H. pylori strains. This further illustrates the relevance of metronidazole-resistant H. pylori in NUD patients. The significantly higher percentage of metronidazole-resistant H. pylori isolates in NUD patients may be attributed to the protection offered by the mucus layer of the nonulcerated stomach to the bacteria that reside below it, resulting in organism exposure to sublethal concentrations of metronidazole and leading to the induction of metronidazole resistance. The results demonstrate that the H. pylori isolates colonizing NUD patients are more likely to be resistant to metronidazole. It will therefore be useful to reevaluate the use of metronidazole in the treatment of NUD patients infected with H. pylori.