Genotypic and phenotypic stability of Helicobacter pylori markers in a nine-year follow-up study of patients with noneradicated infection.

The cagA gene, alleles of the vacA gene,random amplified polymorphic DNA (RAPD), and neutrophil activating capacity (HpNAC) were used to examine paired H. pylori isolates from 10 noneradicated individuals 9 years apart. Paired isolates from each patient were indistinguishable with regard to vacA alleles, RAPD, and HpNAC. Isolates from nine patients showed concordance for the cagA gene, which was not detected in the recent isolate of the tenth patient. Antibodies to CagA were, however, 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 patients. The present study suggests a greater stability of phenotypic and genotypic markers of H. pylori than previously regarded. This might be true for a community with low infection and transmission rates. Complementary techniques like microarrays might, however, disclose evolutionary changes not identified here.