Pharmacology · single question
A duodenal ulcer is most commonly caused by which organism?
Show answer and explanation
Correct answer: D. Helicobacter pylori
- A. ❌ S. mutans is the principal cariogenic organism and plays no role in peptic ulceration.
- B. ❌ E. coli causes urinary tract and gastrointestinal infections but is not the ulcer organism.
- C. ❌ C. difficile causes antibiotic-associated pseudomembranous colitis — a real dental concern after clindamycin, but not an ulcer cause.
- D. ✅ CORRECT — HELICOBACTER PYLORI, a spiral gram-negative urease-producing organism, causes the great majority of duodenal ulcers (roughly 90%) and most gastric ulcers. Urease neutralizes gastric acid locally and allows colonization. It is also a risk factor for gastric adenocarcinoma and MALT lymphoma.
Note: Treatment is triple therapy: a PPI + clarithromycin + amoxicillin (or metronidazole). NSAIDs are the other major ulcer cause — relevant when choosing analgesics.