[Helicobacter pylori: pathogens, pathomechanisms and epidemiology].

H. pylori organisms are microaerophilic gram-negative curved or spiral bacteria that live in the mucus layer of the gastric epithelium. Since the discovery of H. pylori similar organisms have been found in humans (H. cinaedi, H. fennelliae, H. heilmanii) and animals. H. pylori causes chronic active gastritis and is an important factor in the development of peptic ulceration and gastric cancer. Narrow host range, tissue specificity and chronic inflammation are characteristic features. Putative virulence factors of H. pylori are structural components (flagella, adhesins...) extracellular bacterial products (urease, protease, phospholipase, cytotoxin...), induction of autoimmune reactions and the activation or stimulation of cellular products (PAF, interleukins, TNF alpha...). Colonization with H. pylori is common throughout the world; it is likely that one half of the world's population is infected. In developed countries few infections occur during childhood, whereas in developing countries most persons are infected by the age of 10 years. Socioeconomic factors seem to determine the age of acquisition. Person to person spread is the most likely form of transmission, but it is not clear whether this is fecal-oral or oral-oral. No non-human reservoir has been identified so far.