Impact of Helicobacter pylori resistance to clarithromycin on the efficacy of the omeprazole-amoxcillin-clarithromycin therapy

Background: Helicobacter pylori resistance to clarithromycin is relatively frequent in France and is assumed to be the main cause of failure of the proton pump inhibitor-amoxicillin-clarithromycin (proton pump inhibitor-AC) therapy, which is the first-line regimen in France. Aim: To determine the respective effects of clarithromycin primary and secondary resistances on efficacy of the proton pump inhibitor-AC regimen and to determine whether failures are associated with persistence of the same strain or with emergence of a new one. Methods: A total of 123 H. pylori-infected patients were treated for 7 days with omeprazole 20 mg b.d., amoxicillin 1 g b.d., and clarithromycin 500 mg b.d. Eradication was assessed by breath test in 102 patients. Minimal inhibitory concentrations of clarithromycin were determined by E-test. Strain genotyping was performed by random amplified polymorphic DNA. Results: The pre-treatment and post-treatment prevalences of clarithromycin resistance were 19% (23 out of 123) and 69% (nine out of 13), respectively, The rates of eradication were 68% (69 out of 102), 79% (67 out of 85), and 12% (two out of 17) for all, susceptible and resistant strains, respectively. The post-treatment isolate was available for six patients with a susceptible pretreatment isolate and a persistent infection. Resistance emerged in two patients and was associated with persistence of the pre-treatment strain in one and with selection of a new strain in the other. Conclusions: In our hospital, failures of the proton pump inhibitor-AC therapy are related to both clarithromycin primary and secondary resistances, but the emergence of secondary resistance does not explain all of the failures in the initial clarithromycin-susceptible group. In that group a new strain can emerge after failure.