Effect of ornidazole and clarithromycin resistance on eradication of Helicobacter pylori in peptic ulcer disease

Background: Clarithromycin and nitroimidazoles such as metronidazole and or nidazole are among the most frequently used antibiotics for curing Helicoba cter pylori infection. However, controversial data exist on whether their i n vitro resistance has a negative impact on treatment outcome. Methods: Patients with H. pylori positive active peptic ulcer disease were randomly assigned to receive lansoprazole 30 mg o.d., amoxycillin 1 g b.d. and ornidazole 500 mg b.d. (LAO) or lansoprazole 30 mg o.d., amoxycillin 1 g b.d. and clarithromycin 500 mg b.d. (LAC) for 2 weeks. Pre-treatment resi stance to ornidazole and clarithromycin was assessed by Epsilometer (E-) te st. Four weeks after completion of treatment, patients underwent a C-13 ure a breath test to assess H. pylori status. Results: Data from 80 patients with active peptic ulcer disease and positiv e H. pylori status were analysed. The prevalence of primary drug resistance was 25% for metronidazole and 7.5% for clarithromycin. In patients treated with LAO, effective treatment was achieved in 87% of metronidazole-suscept ible, but only 30% of metronidazole-resistant strains (P < 0.01). In the LA C group, therapy was successful in 81% of clarithromycin-susceptible strain s, whereas treatment failed in all patients with primary clarithromycin res istance (n = 3). Conclusion: Resistance against nitroimidazoles significantly affects treatm ent outcome in H. pylori eradication therapy.