Which organism is most commonly associated with gastritis or peptic ulcers?

• A. Campylobacter jejuni
• B. Helicobacter pylori
• C. Salmonella Typhi
• D. Shigella sonnei

Answer: (B)

Helicobacter pylori is the organism most commonly linked to gastritis and peptic ulcers. This curved, gram-negative bacterium survives in the acidic stomach by producing urease, which converts urea to ammonia and raises the local pH, allowing it to colonize the gastric mucosa. The resulting chronic inflammation damages the protective mucous layer and mucosal lining, leading to gastritis and ulcer formation in the stomach or duodenum. The other organisms listed tend to cause different diseases: Campylobacter jejuni causes acute gastroenteritis, Salmonella Typhi causes enteric fever, and Shigella causes dysentery. So the combination of gastric colonization and ulcerative inflammation points to Helicobacter pylori as the best answer.