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Analysis of geospecific markers for Helicobacter pylori variants in patients from Japan and Nigeria by triple-locus nucleotide sequence typing

¹ Laboratory of Enteric Pathogens, Specialist and Reference Microbiology Division, Health Protection Agency, London NW9 5HT, UK
² Department of Endoscopy and Gastrointestinal Endoscopy, National Cancer Centre Hospital, Tokyo 104-0045, Japan
³ The Centre for Digestive Diseases, The General Infirmary at Leeds, Leeds LS1 3EX, UK
⁴ Health Protection Agency Laboratory, York Road, Leeds LS15 7TR, UK

Correspondence
Robert Owen
robert.owen{at}hpa.org.uk

Human migrations and geographical separation over long periods may have resulted in ecologically distinct populations of Helicobacter pylori infecting individuals in different continents. This study used nucleotide sequence analysis with the aim of defining population-specific genomic motifs in isolates from East Asian and African dyspeptic patients. Sequences of internal fragments (542–627 bp) of three housekeeping genes (ureI, ahpC and atpA) were analysed for 85 isolates from individuals in Japan and China (30 isolates), Nigeria and South Africa (14 isolates), the United Kingdom (32 isolates), and nine miscellaneous reference strains. Phylogenetic analyses showed a high degree of intra-set relatedness amongst sequences from the Japanese and Nigerian isolates, with each robustly segregated as distinct lineages irrespective of cagA presence and vacA allelic type. All strains had unique combined sequence types except for identical paired (antrum/corpus) isolates. Population-specific polymorphisms were identified within each gene which were combined to provide unique motifs defining the Japanese and Nigerian regional populations. The alleles were present at variable frequencies in UK and South African isolates. The findings provide unique evidence of positive selection for conserved nucleotide sites linked to the geographical separation in Japan of a strain subpopulation for which we propose the designation H. pylori geovar ‘orientalis’.

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