Abstract
BackgroundHelicobacter pylori is presumed to be co-evolved with its human host and is a highly diverse gastric pathogen at genetic levels. Ancient origins of H. pylori in the New World are still debatable. It is not clear how different waves of human migrations in South America contributed to the evolution of strain diversity of H. pylori. The objective of our 'phylogeographic' study was to gain fresh insights into these issues through mapping genetic origins of H. pylori of native Peruvians (of Amerindian ancestry) and their genomic comparison with isolates from Spain, and Japan.ResultsFor this purpose, we attempted to dissect genetic identity of strains by fluorescent amplified fragment length polymorphism (FAFLP) analysis, multilocus sequence typing (MLST) of the 7 housekeeping genes (atpA, efp, ureI, ppa, mutY, trpC, yphC) and the sequence analyses of the babB adhesin and oipA genes. The whole cag pathogenicity-island (cagPAI) from these strains was analyzed using PCR and the geographic type of cagA phosphorylation motif EPIYA was determined by gene sequencing. We observed that while European genotype (hp-Europe) predominates in native Peruvian strains, approximately 20% of these strains represent a sub-population with an Amerindian ancestry (hsp-Amerind). All of these strains however, irrespective of their ancestral affiliation harbored a complete, 'western' type cagPAI and the motifs surrounding it. This indicates a possible acquisition of cagPAI by the hsp-Amerind strains from the European strains, during decades of co-colonization.ConclusionOur observations suggest presence of ancestral H. pylori (hsp-Amerind) in Peruvian Amerindians which possibly managed to survive and compete against the Spanish strains that arrived to the New World about 500 years ago. We suggest that this might have happened after native Peruvian H. pylori strains acquired cagPAI sequences, either by new acquisition in cag-negative strains or by recombination in cag positive Amerindian strains.
Highlights
Helicobacter pylori is presumed to be co-evolved with its human host and is a highly diverse gastric pathogen at genetic levels
Phylogenetic relationships assessed by fluorescent amplified fragment length polymorphism (FAFLP) genotyping of Peruvian isolates (Figure 1A) revealed 2 different lineages corresponding to the hp-Europe and hsp-Amerind
Representative isolates from both the lineages obtained by FAFLP were subjected to reconfirmation by multilocus sequence typing (MLST) analysis
Summary
Helicobacter pylori is presumed to be co-evolved with its human host and is a highly diverse gastric pathogen at genetic levels. Ancient origins of H. pylori in the New World are still debatable. It is not clear how different waves of human migrations in South America contributed to the evolution of strain diversity of H. pylori. Helicobacter pylori is a Gram-negative bacterium that established itself in the human stomach possibly thousands of years ago [1]. The debate has been further intensified as some studies have posed the possibility that H. pylori infection has some protective effects in esophageal diseases [3]. Possible symbiotic associations have been proposed based on the finding that H. pylori harbor protective, bacteriocin like effect and may be beneficial to its host [5]
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