Helicobacter pylori Infection

A 29-year-old man presents with intermittent epigastric discomfort, without weight loss or evidence of gastrointestinal bleeding. He reports no use of aspirin or nonsteroidal antiinflammatory drugs. A serologic test for Helicobacter pylori is positive, and he receives a 10-day course of omeprazole, amoxicillin, and clarithromycin. Six weeks later, he returns with the same symptoms. How should his case be further evaluated and managed?