[The significance of Helicobacter pylori in medical science].

The discovery of Helicobacter pylori as a dominant cause of gastritis is at least revolutionary both with respect to its clinical consequences as to its contribution to fundamental basic science. The velocity with which basic and clinical experience was accumulated in the H. pylori field has been unsurpassed in medicine. The organism is highly complex and can be divided in two subclasses, a more virulent strain containing the socalled 'pathogenicity island' in addition to vacA and IceA1 antigen and an almost commensal-like subtype. The virulent type in particular is associated with severe inflammation and various clinical disease states. The pathogenesis of duodenal ulcer is well understood. The infection is essentially limited to the antrum causing disturbance of the gastrin homeostasis which is one of the mechanisms leading to enhanced acid production. This constant hyperacidity in the duodenal bulb ultimately leads to development of gastric metaplasia with production of neutral mucus. The latter is essential to allow colonisation with the organism, leading to inflammation, erosion and ultimately ulcer. Curing the infection leads to permanent cure of the ulcer diathesis. The mechanisms that ultimately lead to gastric cancer or gastric Malt lymphoma are less clear. Curing the infection turns out to be more difficult than initially anticipated. Currently the triple therapy (a combination of a proton pump inhibitor with clarithromycin and either amoxycillin or metronidazole), or bismuth triple therapy or bismuth quadruple therapy (a combination of a proton pump inhibitor, bismuth, tetracyclin and metronidazole) are most commonly used. Sadly there is a rising frequency of resistance throughout the world against metronidazole and clarithromycin. Finally increasingly H. pylori infection is considered a model for study of fundamental biological problems such as interaction between organism and host, intracellular signalling in case of infection, evolution of inflammation towards atrophy and cancer etc. Equally interesting is the discovery of novel Helicobacters, such as Helicobacter resistance to bile or Helicobacters responsible for intestinal inflammation.