The most appropriate treatment for this patient is a 10-day course of levofloxacin, amoxicillin, and omeprazole. Helicobacter pylori infection is closely linked with recurrent peptic ulcer disease, chronic metaplastic gastritis, gastric mucosa-associated lymphoid tissue (MALT) lymphoma, gastric adenocarcinoma, iron deficiency anemia, and primary immune thrombocytopenia. Therefore, an effort should be made to successfully eradicate the infection once it is identified. Initial treatment regimens are effective in H. pylori eradication in only 70% to 80% of patients. The most common reason for treatment failure is antibiotic resistance. In the United States, H. pylori resistance prevalence is 37% for metronidazole and 13% for clarithromycin. Clarithromycin resistance is absolute and cannot be overcome by increasing the dose or re-treating with a longer course of therapy. Conversely, metronidazole resistance can be overcome by increasing the dose or by using metronidazole in an alternative medication regimen. If H. pylori infection is not eradicated with primary therapy, as in this patient, a second-line salvage therapy should contain an alternative antibiotic to clarithromycin, and the treatment should be at least 10 days in duration to maximize the likelihood of treatment success. Two universally recommended second-line therapies are (1) a 10- to 14-day course of bismuth subsalicylate, metronidazole, tetracycline, and a proton pump inhibitor (PPI), or (2) a 10-day course of levofloxacin, amoxicillin, and a PPI.