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- Title
Helicobacter pylori virulence genes and microevolution in host and the clinical outcome: review article.
- Authors
Bakhti, Seyedeh Zahra; Latifi-Navid, Saeid; Zahri, Saber
- Abstract
Helicobacter pylori (H. pylori) is the causative agent in development of gastroduodenal diseases, such as chronic atrophic gastritis, peptic ulcers, mucosa associated lymphoid tissue (MALT) lymphoma, and gastric cancer. H. pylori has been associated with inflammation in cardia, showing the fact that infection with this bacterium could also be a risk factor for gastric cardia cancer. Gastric cancer is the fourth most common cancer worldwide. This is the second leading cause of cancer-related deaths, and approximately 700,000 people succumb each year to gastric adenocarcinoma. It has been estimated that 69% of the Iranian population currently harbor H. pylori infection. The prevalence of duodenal ulcer and gastric cancer is high in Iranian populations. However, this has been largely influenced by geographic and/or ethnic origin. Epidemiology studies have shown that host, environmental, and bacterial factors determine the outcome of H. pylori infection. The bacterium contains allelic diversity and high genetic variability into core- and virulence-genes and that this diversity is geographically and ethnically structured. The genetic diversity within H. pylori is greater than within most other bacteria, and its diversity is more than 50-fold higher than that of human DNA. The maintenance of high diversification makes this bacterium to cope with particular challenges in individual hosts. It has been reported that the recombination contributed to the creation of new genes and gene family. Furthermore, the microevolution in cagA and vacA genes is a common event, leading to a change in the virulence phenotype. These factors contribute to the bacterial survival in acidic conditions in stomach and protect it from host immune system, causing tissue damage and clinical disease. In this review article, we discussed the correlation between H. pylori virulence factors and clinical outcomes, microevolution of H. pylori virulence genes in a single host, microevolution of H. pylori during primary infection and progression of atrophic gastritis to adenocarcinoma, and H. pylori infection status in Iran. Finally, we put forward the hypothesis that if the pattern of nucleotide sequence evolution shifts from recombination (r) to mutation (m) and the r/m ratio is reduced, bacterial pathogenicity may be reduced while maintaining the bacterial life. However, this hypothesis should be further studied with future experiments.
- Publication
Tehran University Medical Journal, 2014, Vol 72, Issue 9, p1
- ISSN
1683-1764
- Publication type
Article