Which organism is commonly associated with peptic ulcer disease?

• A. Escherichia coli
• B. Clostridium difficile
• C. Helicobacter pylori
• D. Staphylococcus aureus

Answer: (C)

Peptic ulcer disease is most commonly linked to infection with Helicobacter pylori, a curved Gram-negative bacterium that colonizes the stomach lining. It survives the acidic environment by producing urease, which converts urea to ammonia and raises the local pH, helping the bacteria persist. The resulting inflammatory response damages the protective mucous layer of the stomach or duodenum, making ulcers more likely to form. The other organisms listed are not the classic culprits for peptic ulcers: E. coli typically causes intestinal or urinary infections, Clostridium difficile leads to antibiotic-associated colitis, and Staphylococcus aureus is associated with a range of infections but not the typical scenario of peptic ulcers. Thus, Helicobacter pylori is the organism commonly associated with peptic ulcer disease.