The importance of the level of metronidazole resistance for the success of Helicobacter pylori eradication

AIMS: To evaluate the role of antibiotic susceptibility for the treatment outcome of proton pump inhibitor-dependent and independent Helicobacter pylori eradication regimens. METHODS: In a placebo-controlled clinical study of peptic ulcer patients with H. pylori infection, patients were randomized to receive lansoprazole, clarithromycin and tinidazole twice-daily, clarithromycin and tinidazole once-daily with lansoprazole or with placebo. Helicobacter pylori status was assessed by culture and antibiotic susceptibility by E-test minimal inhibitory concentration (MIC) in 205 clinical isolates. RESULTS: Primary resistance to clarithromycin and metronidazole was 1 and 76%, respectively. In metronidazole susceptible strains eradication rates were similar at > 90% for all treatment groups (P = 0.49). With low-level metronidazole resistance (4 microg/mL < MIC < 256 microg/mL), eradication rates were similar at >75% (P = 0.80). The major difference was found at high-level metronidazole resistance (MIC >or= 256 microg/mL) with 95%, 58% and 21% eradication in the lansoprazole, clarithromycin and tinidazole twice-daily, lansoprazole, clarithromycin and tinidazole once-daily and placebo, clarithromycin and tinidazole once-daily groups, respectively (P < 0.001). CONCLUSION: In the absence of antibiotic resistance, a once-daily therapy of only clarithromycin and tinidazole can achieve a high rate of H. pylori eradication. Such a combination could offer a simpler and cheaper treatment option for developing countries. The standard, twice-daily proton pump inhibitor-based triple therapy was shown to be efficient in H. pylori eradication even in the presence of high-level metronidazole resistance.