<prompt> The causative agent for duodenal ulcer is;ShigellaE. coliH. PyloriLactobacilli  <response>: 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-Hodgkins gastric lymphoma H. pyloriinfection increases the risk of gastric malignancies such asgastric adenocarcinomaandMALTomas 