The effect of antibiotic resistance on the outcome of three 1-week triple therapies against Helicobacter pylori

Background: Resistance of Helicobacter pylori to antibiotics may be a major reason for treatment failure. Aim: To evaluate the effect of primary H. pylori resistance to antibiotics on the cure rates of three anti-H. pylori 1-week triple therapies. Methods: One hundred and sixteen consecutive patients diagnosed H. pylori-positive by gastric histology, rapid urease test and culture were enrolled. Activity of tested antibiotics was determined by means of the E-test. Patients were treated for 7 days with: (i) pantoprazole 40 mg o.d. plus amoxycillin 1 g b.d. and metronidazole 250 mg q.d.s. (PAM); (ii) pantoprazole 40 mg o.d. plus clarithromycin 250 mg b.d. and metronidazole 250 mg q.d.s. (PCM); or (iii) pantoprazole 40 mg o.d. plus amoxycillin 1 g b.d. and clarithromycin 250 mg b.d. (PAC). Two months after completion of therapy, endoscopy and gastric biopsies were repeated. Results: Primary resistance rates to metronidazole, clarithromycin and amoxycillin were 17.2, 6.9 and 0%, respectively. Overall H. pylori cure rates expressed as intention-to-treat and per protocol analyses were, respectively, 79% and 86% with PAM, 82% and 89% with PCM, and 85% and 85% with PAC. Significantly lower cure rates were observed in metronidazole-resistant patients treated with PAM (56% vs. 96%, P = 0.01) or PCM (50% vs. 97%, P = 0.01). A trend towards lower H. pylori cure rates was observed in clarithromycin-resistant patients treated with PCM (67% vs. 91%, P = 0.74) or PAC (50% vs. 87%, P = 0.68). Conclusion: Primary resistance to metronidazole influences the H. pylori cure rate of anti-H. pylori proton pump inhibitor-based triple therapies which include this antibiotic. A similar trend exists for primary clarithromycin resistance.