INTRODUCTIONHelicobacter pylori is recognized as a cause of chronicactive gastritis,gastric and duodenal ulcers,and gastriccancer,though the mechanisms of pathogenesis for H.pylori-associated diseases are not yet well understood.The ecological niche to which H.pylori is well-adapted is INTRODUCTION Helicobacter pylori is recognized as a cause of chronic active gastritis, gastric and duodenal ulcers, and gastric cancer, though the mechanisms of pathogenesis for H. pylori-associated diseases are not yet well. The ecological niche to which H. pylori is well-adapted is