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Abstract

Continuing attempts have been made to classify pathogenic strains within bacterial populations based on DNA fingerprints and to identify virulence factors in H. pylori. We studied 287 H. pylori isolates from patients with duodenal ulcer or gastric cancer from three different geographic regions. DNA fingerprints were generated using REP-PCR and analyzed by cluster analysis. The status of three candidate virulence factors-vacA polymorphism, cagA and iceA,-were examined by PCR amplification. Cluster analysis of the REP-PCR fingerprints showed clustering by geographic region but not by disease presentation. cagA was detected in 91.3% of the isolates. Differences in vacA subtypes were observed among the three geographic regions. There was no association between iceA subtypes and clinical outcome. We conclude that geographic differences among the H. pylori strains exist in single gene allelic variants as well as in the conserved noncoding regions such as REP sequences throughout the entire bacterial genome. We did not detect any association between disease presentation and H. pylori genotypes using either DNA fingerprinting or candidate single gene virulence factors.

Geographic distribution of methyltransferases of Helicobacter pylori: evidence of human host population isolation and migration

“…The cag A gene DNA motifs also presents a clear geographic association, and five types of deletion, insertion, and substitution motifs were found at the 3' end of the H. pylori cag pathogenicity island associated with different human populations [8]. Another study confirms that the candidate virulence factors, vacA , cagA and iceA , cluster according to geographic region [9]. Interestingly, iceA has two known alleles, iceA1 and iceA2 [10,11], with the locus iceA1 encoding a protein with 52% identity with the restriction endonuclease NlaIII [12].…”