Clarithromycin resistance of Helicobacter pylori has a major impact on theefficacy of the omeprazole-amoxicillin-clarithromycin therapy

Clarithromycin resistance of Helicobacter pylori is relatively frequent in France and is assumed to be the main cause of failure of the proton pump in hibitor-amoxicillin-clarithromycin (PPI-AC) therapy, which is the first-lin e regimen in our country. We determined the respective effects of clarithro mycin primary and secondary resistances on efficacy of the PPI-AC regimen a nd examined whether failures were associated with persistence of the same s train or with emergence of a new one. Hundred and twenty three H. pylori-in fected patients were treated for seven days with omeprazole 20 mg b.d., amo xicillin 1 g b.d., and clarithromycin 500 mg b.d. Eradication was assessed by breath test in 102 patients. MICs of clarithromycin were determined by E -test. Strain genotyping was performed by random amplified polymorphic DNA. The pre-treatment and post-treatment prevalences of clarithromycin resista nce were 18.7% (23/123) and 69.2% (9/13), respectively. The rates of eradic ation were 67.6% (69/102), 78.8% (67/85), and 11.8% (2/17) for all, suscept ible and resistant strains, respectively. The post-treatment isolate was av ailable for six patients with a susceptible pre-treatment isolate and a per sistent infection; resistance emerged in two patients and was associated wi th persistence of the pre-treatment strain in one and with selection of a n ew strain in the other. In conclusion, in our hospital, failures of the PPI -AC therapy are related to both clarithromycin primary and secondary resist ances but emergence of secondary resistance does not explain all failures i n the initial clarithromycin-susceptible group. In that group a new strain can emerge after failure. (C) 2001 Editions scientifiques et medicales Else vier SAS.