Abstract
Helicobacter pylori is a gram-negative bacterium that colonizes the stomach of nearly half of the world's population. Genotypic characterization of H. pylori strains involves the analysis of virulence-associated genes, such as vacA, which has multiple alleles. Previous phylogenetic analyses have revealed a connection between modern H. pylori strains and the movement of ancient human populations. In this study, H. pylori DNA was amplified from the stomach tissue of the Kwäday Dän Ts'ìnchi individual. This ancient individual was recovered from the Samuel Glacier in Tatshenshini-Alsek Park, British Columbia, Canada on the traditional territory of the Champagne and Aishihik First Nations and radiocarbon dated to a timeframe of approximately AD 1670 to 1850. This is the first ancient H. pylori strain to be characterized with vacA sequence data. The Tatshenshini H. pylori strain has a potential hybrid vacA m2a/m1d middle (m) region allele and a vacA s2 signal (s) region allele. A vacA s2 allele is more commonly identified with Western strains, and this suggests that European strains were present in northwestern Canada during the ancient individual's time. Phylogenetic analysis indicated that the vacA m1d region of the ancient strain clusters with previously published novel Native American strains that are closely related to Asian strains. This indicates a past connection between the Kwäday Dän Ts'ìnchi individual and the ancestors who arrived in the New World thousands of years ago.
Highlights
Helicobacter pylori is a helical, gram-negative, microaerophilic bacterium that inhabits the stomach of more than 50% of the world’s population [1] and is one of several bacterial microbiota that are capable of colonizing the human stomach [2]
Yamazaki and colleagues analyzed 220 H. pylori strains from the areas of Fukui and Okinawa, Japan to identify a relationship between the vacA gene and the clinical outcome [14]
The similarity of the Tatshenshini H. pylori strain to these ‘Western’ Japanese strains in the proximal region of the vacA m allele suggests that Aboriginal North Americans were exposed to European H. pylori strains prior to AD 1850
Summary
Helicobacter pylori is a helical, gram-negative, microaerophilic bacterium that inhabits the stomach of more than 50% of the world’s population [1] and is one of several bacterial microbiota that are capable of colonizing the human stomach [2]. There is evidence to suggest that H. pylori is mainly transmitted within families, especially from mother to child [4]. This infection is normally acquired in childhood, and the bacterium’s genetic fingerprint remains the same for decades [5]. The virulence of H. pylori is partly determined by the type of vacuolating cytotoxin produced by the organism [7]. This cytotoxin is the result of VacA expression, and the vacA gene is found in all H. pylori strains. The m1 allele is more often linked with symptomatic disease due to the increased binding of the expressed VacA protein to host cells [3]
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