Abstract

Helicobacter pylori is a bacterium that has evolved with humans, is transmitted from person to person and persistently colonizes the stomach. During its long coexistence with humans, H. pylori has developed complex strategies to limit the degree and extent of inflammation and damage to the gastric mucosa. It is capable of altering the physiology and immune response of the host, thereby allowing it to persist throughout life. Infection with H. pylori has been linked to such diseases as severe gastritis, peptic ulcers and gastric cancer. Differences in the incidence of gastric cancer across the world can be attributed to regionally different H. pylori genotypes, dietary factors, environmental factors, and host factors, as well as virulence gene polymorphisms (particularly cagA and vacA) in different strains. The colonization of an individual by more than one strain of H. pylori is common, and a recurrent infection during childhood provides substrates for the acquisition or recombination of new genetic sequences. This review explores the evolutionary history of H. pylori during infection recurrence and the genetic diversity in humans as well as in an animal model.

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