Which organism is not a common etiologic agent of peptic ulcers?

• A. Escherichia coli
• B. Helicobacter pylori
• C. Shigella dysenteriae
• D. Bordetella pertussis

Answer: (D)

Peptic ulcers arise mainly from damage to the stomach or duodenal lining due to acid, with Helicobacter pylori infection and NSAID use being the most common causes. Among bacteria, those that typically interact with the GI tract in a way that could lead to mucosal injury would be considered potential culprits, but their usual disease patterns differ by location. Escherichia coli and Shigella dysenteriae are primarily enteric pathogens that affect the intestines and cause dysentery or gastroenteritis rather than gastric ulcers. Bordetella pertussis, on the other hand, is a respiratory organism known for causing whooping cough and does not inhabit or injure the gastric mucosa. Therefore, Bordetella pertussis is not a common etiologic agent of peptic ulcers.