Association of Helicobacter pylori with gastroduodenal diseases.

Helicobacter pylori was first cultured in vitro in 1982. This bacterium is a spiral gram-negative rod which grows under microaerophilic conditions. The ecological niche is the mucosa of the human stomach which had been thought to be aseptic before the discovery of this bacterium. This organism causes a long-lasting infection throughout a person's life if there is no medical intervention. Numerous persons are infected with the organism around the world, and the rate of infection in Japan is nearly 50% of the population. However, the route of infection remains unclear because the organism has not been isolated from any environment other than several animals. H. pylori is now recognized as a causative agent of gastritis and peptic ulcers. Though gastritis, and especially chronic active gastritis, is observed at least histologically in all persons with H. pylori, peptic ulcers develop in only some infected persons. Specific factors in the host and/or the bacteria are needed for the development of peptic ulcer disease. Furthermore, H. pylori is considered to be related to the development of gastric mucosa-associated lymphoid tissue (MALT) lymphoma, especially those of low grade. Also, H. pylori infection is a major determinant for initiating the sequence of events leading to gastric cancer. In some patients with low-grade gastric MALT lymphoma, the eradication of H. pylori led to a regression of lesion. Gastric cancer has been induced in Mongolian gerbils with long-term H. pylori infection. The combinations of drugs, which consist of an antisecretory agent (acid-suppressing agent) and antimicrobial agents, are used for the eradication of the organism. Eradication therapy is recommended at least for patients with peptic ulcers.