|World-wide studies of H. pylori isolates from different geographical regions demonstrated weak clonal groupings and geographical partitioning of H. pylori isolates (Achtman et al., 1999; Carroll et al., 2003). [...] Should recombination only occur between a resident H. pylori population, exchange of genetic sequences can homogenise this population. The introduction of polymorphisms and sequence variants from one H. pylori population specific to a particular geographical region to another H. pylori population from a different geographical region via human migration makes the association of particular genotypes with specific geographical locations more difficult. Although this introduction of new polymorphisms into a particular H. pylori population poses a problem with identifying specific genotypes within certain geographical locales, it may, provide information on the ancestry of the hosts. Different studies have been aimed at identifying whether H. pylori was introduced to Latin America via European or Asian migrant populations (Kersulyte et al., 2000; Ghose et al., 2002). However, a recent study by Falush et al. (Falush et al., 2003b) showed that sequence analysis of H. pylori isolates obtained from 27 countries displayed geographical partitioning.
Achtman, M., T. Azuma, D. E. Berg, Y. Ito, G. Morelli, Z. J. Pan, S. Suerbaum, S. A. Thompson, A. van der Ende, and L. J. van Doorn, Recombination and clonal groupings within Helicobacter pylori from different geographical regions, Mol Microbiol, 32, 459-470, 1999.
Carroll, I. M., N. Ahmed, S. M. Beesley, A. A. Khan, S. Ghousunnissa, C. A. Moráin, and C. J. Smyth, Fine-structure molecular typing of Irish Helicobacter pylori isolates and their genetic relatedness to strains from four different continents, J Clin Microbiol, 41, 5755-5759, 2003.
Falush, D., T. Wirth, B. Linz, J. K. Pritchard, M. Stephens, M. Kidd, M. J. Blaser, D. Y. Graham, S. Vacher, G. I. Perez-Perez, Y. Yamaoka, F. Mégraud, K. Otto, U. Reichard, E. Katzowitsch, X. Wang, M. Achtman, and S. Suerbaum, Traces of human migrations in Helicobacter pylori populations, Science, 299, 1582-1585, 2003b.
Ghose, C., G. I. Perez-Perez, M. G. Dominguez-Bello, D. T. Pride, C. M. Bravi, and M. J. Blaser, East Asian genotypes of Helicobacter pylori strains in Amerindians provide evidence for its ancient human carriage, Proc Natl Acad Sci U S A, 99, 15,107-15,111, 2002.
Kersulyte, D., A. K. Mukhopadhyay, B. Velapatiño, W. Su, Z. Pan, C. Garcia, V. Hernandez, Y. Valdez, R. S. Mistry, R. H. Gilman, Y. Yuan, H. Gao, T. Alarcón, M. López-Brea, G. Balakrish Nair, A. Chowdhury, S. Datta, M. Shirai, T. Nakazawa, R. Ally, I. Segal, B. C. Wong, S. K. Lam, F. O. Olfat, T. Borén, L. Engstrand, O. Torres, R. Schneider, J. E. Thomas, S. Czinn, and D. E. Berg, Differences in genotypes of Helicobacter pylori from different human populations, J Bacteriol, 182, 3210-3218, 2000.
|In addition, worldwide studies encompassing H. pylori isolates from many geographic regions have demonstrated weak clonal groupings and geographic partitioning of H. pylori isolates [9,17]. If recombination only occurs between a resident H. pylori population, exchange of genetic sequences can genetically homogenise this population. [...]
Introduction of polymorphisms and sequence variants from one H. pylori population from a particular geographic region to another H. pylori population from another geographic region via human migration makes the association of particular genotypes with specific geographic locations more difficult. Although the introduction of new polymorphisms into a particular H. pylori population poses a problem with identifying specific genotypes within certain geographic locales, it may, however, provide information on the ancestry of the hosts in whose stomachs the strains were carried. Studies have been aimed at demonstrating the path of human migration to Latin America with conflicting results regarding whether European or Asian populations brought H. pylori to South America [16,11]. However, a recent and comprehensive study by Flaush [sic] et al.  demonstrated that sequence analysis of H. pylori isolates recovered from twenty-seven countries displayed geographic partitioning.
9. Achtman M, Azuma T, Berg DE, Ito Y, Morelli G, Pan ZJ, Suerbaum S, Thompson SA, van der Ende A, van Doorn LJ: Recombination and clonal groupings within Helicobacter pylori from different geographical regions. Mol Microbiol 1999, 32:459-470.
11. Go MF: Helicobacter pylori: its role in ulcer disease and gastric cancer and how to detect the infection. Acta Gastroenterol Latinoam 1996, 26:45-49.
16. Kersulyte D, Mukhopadhyay AK, Velapatino B, Su W, Pan Z, Garcia C, Hernandez V, Valdez Y, Mistry RS, Gilman RH, Yuan Y, Gao H, Alarcon T, Lopez-Brea M, Balakrish Nair G, Chowdhury A, Datta S, Shirai M, Nakazawa T, Ally R, Segal I, Wong BC, Lam SK, Olfat FO, Boren T, Engstrand L, Torres O, Schneider R, Thomas JE, Czinn S, Berg DE: Differences in genotypes of Helicobacter pylori from different human populations. J Bacteriol 2000, 182:3210-3218.
17. Ahmed N, Khan AA, Alvi A, Tiwari S, Jyothirmayee CS, Kauser F, Ali M, Habibullah CM: Genomic analysis of Helicobacter pylori from Andhra Pradesh, South India: Molecular evidence for three major genetic clusters. Curr Sci 2003, 85:101-108.
19. Falush D, Wirth T, Linz B, Pritchard JK, Stephens M, Kidd M, Blaser MJ, Graham DY, Vacher S, Perez-Perez GI, Yamaoka Y, Megraud F, Otto K, Reichard U, Katzowitsch E, Wang X, Achtman M, Suerbaum S: Traces of human migrations in Helicobacter pylori populations. Science 2003, 299:1582-1585.
40. Carroll IM, Ahmed N, Beesley SM, Khan AA, Ghousunnissa S, O'Morain CA, Smyth CJ: Fine-structure molecular typing of Irish Helicobacter pylori isolates and their genetic relatedness to strains from four different continents. J Clin Microbiol 2003, 41:5755-5759.