cqvip:The cagA gene, alleles of the vacA gene, random amplified polymorphic DNA (RAP D), and neutrophil activating capacity (HpNAC) were used to examine paired H. py lori is- olates from 10 noneradicated individuals 9 years apart. Paired isolates from e ach patient were indistinguishable with regard to vacA alleles, RAPD, and HpNAC. Isolates fromnine patients showed concordance for the cagA gene, which was not detected in the recent isolate of the tenth patient. Antibodies to CagA were,how ever, demonstrated in the serum specimens 9 years apart and were also present in two other patients whose paired isolates were cagA-, indicating the existence of both cagA+and cagA-organisms, with the latter predominating in some patient s.The present study suggests a greater stability of phenotypic and genotypic mar kers of H. pylori than previously regarded. This might be true for a community w ith low infection and transmission rates. Complementary techniques like microarr ays might,however, disclose evolutionary changes not identified here.
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