Review Question - QID 212312

A 66-year-old man presents to the office complaining of abdominal pain. He reports that the pain is mid-epigastric and “gnawing.” It worsens after meals but improves “somewhat” with antacids. The patient’s medical history is significant for hypertension, hyperlipidemia, and gout. He takes aspirin, lisinopril, atorvastatin, and allopurinol. He uses ibuprofen during acute gout attacks and takes over the counter multivitamins. He also started drinking ginkgo tea once a week after his wife saw a news story on its potential benefits. The patient has a glass of whiskey after work 2 nights a week but denies tobacco or illicit drug use. An upper endoscopy is performed that reveals a gastric ulcer. A urease breath test is positive for Heliobacter pylori. The patient is prescribed bismuth subsalicylate, omeprazole, metronidazole, and tetracycline for 2 weeks. At follow-up, the patient continues to complain of abdominal pain. He has taken all his medications as prescribed along with 10-12 tablets of antacids a day. He denies hematemesis, hematochezia, or melena. Biopsy from the previous upper endoscopy was negative for malignancy. A repeat urease breath test is positive. Which of the following is the most likely cause for the patient’s poor treatment response?