In the tailored regimen group, patients infected with a clarithromycin-sensitive strain of H. pylori are treated with triple therapy consisting of clarithromycin 200 mg tid, amoxicillin 500 mg tid and the individualized doses of lansoprazole dose (i.e., 30 mg tid in RMs, 15 mg tid in IMs, and 15 mg bid in PMs) for one week, while patients infected with a clarithromycin-resistant strain of H. pylori are treated with dual therapy consisting of amoxicillin 500 mg qid and the individualzed dose of lansoprazole (i.e., 30 mg qid in RMs, 15 mg qid in IMs, and 15 mg bid in PMs) for two weeks.