Which bacterium is most commonly associated with gastric ulcers?

Helicobacter pylori is the bacterium most commonly associated with gastric ulcers due to its unique ability to survive in the acidic environment of the stomach. It colonizes the stomach lining and can lead to inflammation, known as gastritis, which can contribute to the development of both gastric and duodenal ulcers. H. pylori produces urease, an enzyme that converts urea into ammonia and bicarbonate, which helps neutralize stomach acid and create a more hospitable environment for the bacteria. This persistent infection can provoke an immune response that further damages the gastric epithelium, resulting in ulcer formation.

Given this specific pathogenic role in ulcer disease, H. pylori is well-established in medical literature as the primary bacterial cause of gastric ulcers, differentiating it significantly from the other listed bacteria that are associated with different diseases or conditions.