[Epidemiology and pathogenesis of Helicobacter pylori infection]

In 1982 a spiral gram-negative bacterium was first cultured from human gastric mucosa. Helicobacter pylori causes chronic active gastritis, which is the most common chronic infectious disease worldwide. The fact that this bacterial infection is furthermore linked to the majority of all duodenal and gastric ulcers is now commonly accepted after initial scepticism. Some fundamentals of this infectious disease like the extrahuman reservoir of pathogens and the mode of transmission are only partially understood. Some of the bacterial virulence factors allowing mucosal colonization and inflammation have been described. So are some details in the bacterial interaction with the host's immune system. The specific feature of this infection is the inability of the immune system to eliminate H. pylori. Finally no immunity but lifelong chronic infection results. The question, why some individuals infected will have merely gastritis, while others will suffer from peptic ulcer disease, or even gastric carcinoma cannot be answered sufficiently by now. Environmental factors may play a role as well as varying pathogenicity of bacterial strains. Furthermore the age at which infection was acquired and genetic differences in the host's susceptibility to disease are of importance.