It is valuable to extend genotyping studies of Helicobacter pylori to strains from indigenous communities across the world to better define adaption, evolution, and associated diseases. We aimed to genetically characterize both human individuals and their infecting H. pylori from indigenous communities of Mexico, and to compare them with those from other human groups. We studied individuals from three indigenous groups, Tarahumaras from the North, Huichols from the West and Nahuas from the center of Mexico. Volunteers were sampled at their community site, DNA was isolated from white blood cells and mtDNA, Y-chromosome, and STR alleles were studied. H. pylori was cultured from gastric juice, and DNA extracted for genotyping of virulence and housekeeping genes. We found Amerindian mtDNA haplogroups (A, B, C, and D), Y-chromosome DYS19T, and Amerindian STRs alleles frequent in the three groups, confirming Amerindian ancestry in these Mexican groups. Concerning H.pylori cagA phylogenetic analyses, although most isolates were of the Western type, a new Amerindian cluster neither Western nor Asian, was formed by some indigenous Mexican, Colombian, Peruvian and Venezuelan isolates. Similarly, vacA phylogenetic analyses showed the existence of a novel Amerindian type in isolates from Alaska, Mexico and Colombia. With hspA strains from Mexico and other American groups clustered within the three major groups, Asian, African or European. Genotyping of housekeeping genes confirmed that Mexican strains formed a novel Asian-related Amerindian group together with strains from remote Amazon Aborigines. This study shows that Mexican indigenous people with Amerindian markers are colonized with H. pylori showing admixture of Asian, European and African strains in genes known to interact with the gastric mucosa. We present evidence of novel Amerindian cagA and vacA alleles in indigenous groups of North and South America.
Background:The cagA gene is a marker for the presence of the cag pathogenicity island, and the presence of cagA positive strains of Helicobacter pylori can identify individuals with a higher risk of developing gastrointestinal diseases. Aims: To study the interaction between H pylori cagA(+) and cagA(2) strains and the gastric mucosa. Methods: Patients with H pylori associated gastritis and peptic ulcers were studied. Biopsies were obtained from the antrum, corpus, fundus, and incisura for H pylori culture, and for in situ hybridisation studies. From each biopsy, multiple single H pylori colonies were isolated and propagated for DNA isolation, and cagA was detected by the polymerase chain reaction (PCR). For in situ detection of H pylori an oligonucleotide specific for an H pylori common antigen and an oligonucleotide specific for cagA were used as probes. Biotinylated probes were incubated with biopsy sections, developed with streptavidinhorseradish peroxidase, and amplified with the tyramide system. Results: PCR results for cagA in isolated colonies confirmed the in situ hydridisation studies. In situ hybridisation identified cagA(+) bacteria in patients with cagA(+) isolates; cagA(2) bacteria in patients with cagA(2) isolates, and cagA(+) and cagA (2) bacteria in patients with both cagA(+) and cagA (2) isolates. CagA(2) bacteria usually colonised the mucous gel or the apical epithelial surface, whereas cagA(+) bacteria colonised the immediate vicinity of epithelial cells or the intercellular spaces. Conclusions: These results document a different in vivo interaction between H pylori cagA(+) or cagA(2) strains and the gastric mucosa.
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