Prevalence of resistance to clarithromycin and its clinical impact on the efficacy of Helicobacter pylori eradication

Background: Triple therapy with a proton-pomp inhibitor (PPI) in combinatio n with metronidazole and clarithromycin is the method of choice for eradica tion of Helicobacter pylori. Failures have been primarily blamed on the dev elopment of resistance to clarithromycin. The present study investigated th e prevalence and clinical significance of resistance to clarithromycin and metronidazole in determining therapeutic success of both triple therapy as a primary eradication method and high-dose dual therapy in non-responders. Methods: On the basis of prior therapy, H, pylori-positive patients were as signed to one of two groups in the present prospective study. Group A (n = 93) included patients who had not undergone any prior eradication treatment , whereas group B (n = 15) consisted of patients who had received clarithro mycin but in whom eradication had been unsuccessful. All patients underwent endoscopy with biopsy for bacterial culture and resistance studies. Patien ts in group A were treated with a 7-day regimen of pantoprazole (40 mg twic e daily), metronidazole (500 mg twice daily), and clarithromycin (250 mg tw ice daily), whereas those in group B received omeprazole (40 mg three times a day) and amoxycillin (1000 mg three times a day) for 14 days. Success of the eradication treatment was ascertained by means of the C-13 urea breath test. Results: In group A resistance to clarithromycin and metronidazole w as identified in 3 patients (4.9%) and in 14 patients (22.9%), respectively . Eradication proved successful in 78 of 84 patients (92.6%) followed up. T wo of the 3 patients with primary clarithromycin resistance and 1 of the 14 patients with metronidazole resistance did not respond to treatment. In gr oup B isolated or combined resistance to clarithromycin was found in seven patients, whereas another four showed isolated resistance to metronidazole. Eradication proved successful in 10 of 13 controlled patients (76.9%) foll owed up, and only 2 patients reported severe side effects. Conclusion: Dete rmination of antibiotic resistance before initiating therapy is not necessa ry, since primary resistance to clarithromycin is rare. The Italian triple therapy remains a highly effective primary therapeutic method. Further, rou tine determination of resistance in non-responders also seems to be superfl uous because high-dose dual therapy is an effective and well-tolerated seco nd-line therapy regardless of the patients' resistance status.