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 ( Helicobacter pylori is a gram-negative spiral microorganism that is closely associated with gastritis and peptic ulcer (PU) diseases. It was noted that a substantial number of subjects with nonulcer dyspepsia (NUD) also harbor the bacterium. The triple therapy used to treat H. pylori infection, consisting of bismuth subsalicylate and two antibiotics, usually metronidazole and tetracycline or amoxicillin, has been found to result in an eradication rate of approximately 90% (18). However, the effect of this treatment was found to be compromised when the patient harbors H. pylori isolates that are drug resistant (15,16,19). The prevalence of resistance to metronidazole has increased or remained steady over the past few years in several countries, including Singapore (3, 4, 6).The disk diffusion test is routinely used to determine sensitivities to antibiotics, as it is economical and easy to perform (17). However, the agar dilution method, although tedious to perform, is still the reference method for the testing of antibiotic susceptibility (13). This method not only determines the antibiotic susceptibility but also the MICs for the bacteria. The commercially available E-test is a method that combines the advantages of the disk diffusion and agar dilution methods, as it is easy to use and also provides the MICs for the bacteria tested (5). However, the E-test is a commercial kit and for routine use is more costly than the agar dilution method, and studies have shown discrepancies in the results obtained by the two methods (1,14).In this study, we examined the relevance of metronidazole resistance in patients with PU and NUD, while the agar dilution method was used to determine the MICs for the H. pylori isolates. MATERIALS AND METHODSProcessing of biopsy specimens. A total of 211 consecutive patients with dyspeptic symptoms were included in this study. Of these, 115 patients had PU, while 96 patients had NUD. PUs include duodenal or gastric ulcers, or both, while NUD is defined as dyspeptic symptoms but a lack of endoscopic evidence of an ulcer (27). The ages of the patients ranged from 17 to 86 years, with an average age of 45.7 years. Of the 211 patients, 133 were males and 78 were females. The study included 175 Chinese, 14 Malays, 14 Indians, and 8 patients of other ethnicities. Informed...