Implications of molecular genotyping of Helicobacter pylori isolates from different human populations by genomic fingerprinting of enterobacterial repetitive intergenic consensus regions for strain identification and geographic evolution.

Biogeographic partitioning of the genome is typical of the gastric pathogen Helicobacter pylori. Such population-specific evolution could serve as a model for understanding host-pathogen interaction and the impact of genetic drift and recombination on insular populations. With a total of 320 isolates from six geographic regions (Japan, India, England, Spain, Ireland, Africa, and Peru) analyzed by enterobacterial repetitive intergenic consensus (ERIC)-based genotyping, we examined genetic affinities among various H. pylori populations in the world. Several strain-specific and region-specific differences were observed by ERIC-based typing. Polymorphic ERIC patterns indicated that the ERIC sequences are in fact dispersed in the H. pylori chromosome at different locations separated by various distances. Phylogenetic analysis of 61 representative isolates revealed three distinct genetic clusters populated by isolates with shared ERIC types independent of the cag right-junction motif type and vacA allele status. Among the notable genetic relationships were the genotypic similarities between Irish and Japanese and between Peruvian and Japanese isolates. Insular genotypic characteristics of Irish isolates amid genetic similarity to East Asian, as well as North European, strains have been once again proved in this study. Peruvian genotypes were more similar to those of Japanese isolates than to those of Iberian or European isolates. Given the current debate on the origin and age of present-day H. pylori, this is a significant finding that supports the possibility of ancient colonization of Amerindians with East Asian strains. Genotypic data presented here will be additionally helpful in realizing the importance of H. pylori geographical genomics in the development of gastroduodenal pathology.