[Ulcer--an infection?].

In the past gastric acid was considered to be the major factor in the pathogenesis of peptic ulcers. For the first time bacteria were found in the stomach at the end of the last century. However, Helicobacter pylori could be detected and characterized not before 1983. Specific factors of virulence enable H. pylori to colonize the gastric mucosa. Infection occurs during childhood and due to a cohort-phenomenon the prevalence increases continuously with age. H. pylori infection can be diagnosed in about 95% of patients with duodenal ulcer and 70% of gastric ulcers. The important pathogenetic role of H. pylori infection could be demonstrated in eradication trials. According to our present knowledge gastric acid and H. pylori are independent prerequisits in peptic ulcer pathogenesis. H. pylori negative ulcer derive from NSAIDs or from the rare Zollinger-Ellison syndrome.