Genetic heterogeneity of Helicobacter pylori by pulse-field gel electrophoresis and re-evaluation of DNA homology

Abstract

Purpose: The genetic heterogeneity of Helicobacter pylori isolates was re-evaluated by using pulse-field gel electrophoresis to examine macrorestriction patterns and by studying DNA homology.

Materials and methods: Twenty H. pylori isolates, two closely related species, H. mustelae and H. felis, and Campylobacter spp. were used. Notl-digested macrorestriction patterns were examined by pulse-field gel electrophoresis. DNA homology was examined by the S1 nuclease method, using [3H]-labeled DNA from H. pylori NCTC11637 and two H. pylori isolates for reference.

Result: Intergenus DNA homology between H. pylori and Campylobacters was 50-60%. Interspecies homology between H. pylori and H. mustelae or H. felis was around 60%. Intraspecies homology among H. pylori isolates 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. Notl pulse-field gel electrophoresis patterns of H. pylori isolates differed markedly at the individual strain level. There was no specific relationship to any deviation from DNA homology, and the differences were observed within rather homogeneous members of the species.

Conclusion: The polymorphism in the Notl pulse-field gel electrophoresis patterns of H. pylori isolates differed markedly among strains, even though these isolates displayed species homogeneity, with DNA homology of 70-100%.