GENETIC-HETEROGENEITY OF HELICOBACTER-PYLORI BY PULSE-FIELD GEL-ELECTROPHORESIS AND REEVALUATION OF DNA HOMOLOGY

Purpose: The genetic heterogeneity of Helicobacter pylori isolates was re-evaluated by using pulse-field gel electrophoresis to examine macr orestriction patterns and by studying DNA homology. Materials and meth ods: Twenty H. pylori isolates, two closely related species, H. mustel ae and H. felis, and Campylobacter spp. were used. Notl-digested macro restriction patterns were examined by pulse-field gel electrophoresis. DNA homology was examined by the S1 nuclease method, using [H-3]-labe led DNA from H. pylori NCTC11637 and two H. pylori isolates for refere nce. Result: Intergenus DNA homology between H. pylori and Campylobact ers was 50-60%. Interspecies homology between H. pylori and H. mustela e or H. felis was around 60%. Intraspecies homology among H. pylori is olates was above 80%, except for a few that exhibited 70-80% homology. These findings indicate that all H. pylori isolates were homogeneous and belonged to the same species. Nod pulse-field gel electrophoresis patterns of H. pylori isolates differed markedly at the individual str ain level. There was no specific relationship to any deviation from DN A homology, and the differences were observed within rather homogeneou s members of the species. Conclusion: The polymorphism in the Notl pul se-field gel electrophoresis patterns of H. pylori isolates differed m arkedly among strains, even though these isolates displayed species ho mogeneity, with DNA homology of 70-100%.