Helicobacter pylori: the versatile pathogen.

Helicobacter pylori is a curvilinear motile gram-negative bacillus which is now recognized as the principal cause of type B gastritis, duodenal ulcer, gastric ulcer and MALT lymphoma. There is also a high degree of association between H. pylori gastritis and gastric carcinoma and non-Hodgkin's lymphoma of the stomach. H. pylori infection of the stomach is the most frequent chronic infection in the world. H. pylori is an extraordinary pathogen with virtually unrivaled versatility. The organism possesses the capacity to colonize and prosper in the hostile acidic gastric lumen, an environment in which other microorganisms cannot survive. H. pylori contains and expresses an assortment of proinflammatory biomolecules. H. pylori also stimulates host cells to release proinflammatory substances which participate in the initiation and perpetuation of inflammation and tissue injury. H. pylori elaborates a potent urease and a variety of other enzymes necessary for colonization and expression of the organism's pathogenicity. H. pylori is usually acquired in childhood, believed usually by fecal-oral transmission. The principal lesion induced by H. pylori is type B gastritis, which begins as acute inflammation involving the antrum. Type B gastritis then extends to the entire stomach with gradual progression to chronic gastritis and variable degrees of gastric mucosal atrophy. Much now is known but much more remains to be learned about H. pylori and the diseases which this extraordinary pathogen produces.