The causative agent for duodenal ulcer is;

H. Pylori is gram negative bacteria, non-spore forming, micro aerophilic, extra cellular bacteria. H. pylori causes Peptic ulcer disease (80% of duodenal ulcer and 60% of gastric ulcer) It acts by decreasing Somatostatin - producing D cells. Other diseases caused by it are - Chronic atrophic gastritis and Autoimmune gastritis Adenocarcinoma of stomach (non cardiac) and non-Hodgkin's gastric lymphoma H. pyloriinfection increases the risk of gastric malignancies such asgastric adenocarcinomaandMALToma's