Quadruple therapy containing amoxicillin and tetracycline is an effective regimen to rescue failed triple therapy by overcoming the antimicrobial resistance of Helicobacter pylori

Aim: To identify optimal antibiotics for second-line quadruple therapy of Helicobacter pylori after failed 1-week triple therapy. Methods: One hundred patients were enrolled in this study after the failure of 1-week triple therapy. They were randomized to receive 1-week quadruple therapy consisting of amoxicillin, omeprazole and bismuth salts, plus either metronidazole or tetracycline. Before quadruple therapy, the H. pylori culture of each patient was tested for metronidazole resistance or clarithromycin resistance by E-test. Six weeks later, an endoscopy or ¹³C-urea breath test was used to define the success of H. pylori eradication. Results: The H. pylori eradication rates by intention-to-treat and per protocol analysis were higher in the tetracycline group than in the metronidazole group (intention-to-treat: 78% vs. 58%, P < 0.05; per protocol: 89% vs. 67%, P < 0.05). In the metronidazole group, but not in the tetracycline group, the per protocol eradication rate of quadruple therapy was lower for the infected isolates with metronidazole resistance than for those without metronidazole resistance (77% vs. 33%, P < 0.05). Conclusion: Quadruple therapy, including tetracycline and amoxicillin, improves the H. pylori eradication rate after failed triple therapy.