Chromosomal heterogeneity of Helicobacter pylori isolates by pulsed-field gel electrophoresis.

The genome of 24 Helicobacter pylori (H. pylori) isolates was analyzed by restriction endonuclease digestion and pulsed-field gel electrophoresis (PFGE). On PFGE profiles of NotI, 12 isolates among 24 yielded four to nine fragments which differed among them. The other 12 isolates could not be digested with NotI. The total genome size calculated from individual fragments ranged from 1.04 x 10(3) to 1.80 x 10(3) kb. This remarkable uneveness in the total genome size among isolates is unusual if H. pylori is considered a single species. Therefore, the extreme diversity in PFGE profiles and genome size among H. pylori strains, which had been considered as homogeneous according to conventional biochemical criteria, led us to reexamine the H. pylori species for their genomic homology. Furthermore, we used the genetic heterogeneity as a marker to identify specified strains among clinical isolates.