Distinctiveness of Genotypes ofHelicobacter pyloriin Calcutta, India

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Abstract
The genotypes of 78 strains ofHelicobacter pylorifrom Calcutta, India (55 from ulcer patients and 23 from more-benign infections), were studied, with a focus on putative virulence genes and neutral DNA markers that were likely to be phylogenetically informative. PCR tests indicated that 80 to 90% of Calcutta strains carried thecagpathogenicity island (PAI) and potentially toxigenicvacAs1alleles of the vacuolating cytotoxin gene (vacA), independent of disease status. This was higher than in the West (wherecagPAI+vacAs1genotypes are disease associated) but lower than in east Asia. TheiceA2gene was weakly disease associated in Calcutta, whereas in the West the alternative but unrelatediceA1gene at the same locus is weakly disease associated. DNA sequence motifs ofvacAm1(middle region) alleles formed a cluster that was distinct from those of east Asia and the West, whereas thecagAsequences of Calcutta and Western strains were closely related. An internal deletion found in 20% of CalcuttaiceA1genes was not seen in any of ∼200 strains studied from other geographic regions and thus seemed to be unique to thisH. pyloripopulation. Two mobile DNAs that were rare in east Asian strains were also common in Calcutta. About 90% of Calcutta strains were metronidazole resistant. These findings support the idea thatH. pylorigene pools differ regionally and emphasize the potential importance of studies of Indian and other non-WesternH. pyloripopulations in developing a global understanding of this gastric pathogen and associated disease.

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