Microbiological aspects of Helicobacter pylori infection.

Helicobacter pylori colonises the human gastroduodenal mucosa, causes chronic active gastritis, is a co-factor for the development of duodenal ulceration, and is associated with gastric ulceration and gastric cancer. As there are no readily available typing schemes for identification of individual isolates, little is known about the acquisition, distribution and frequency of particular strains of H. pylori in different populations, communities and families. Molecular (DNA) typing studies carried out over the last three years on isolates from the United Kingdom and other countries at the National Collection of Type Cultures (NCTC) show considerable diversity in strains from different individuals, yet multiple isolates from different gastroduodenal sites in an individual are usually identical. Major routes of infection have not been established, but similarities of DNA sequence between isolates from some family members, and the serological data, indicate that some H. pylori infections are acquired in households during childhood. Molecular typing will have an important role in future studies on transmission.