Molecular evolution of the seventh-pandemic clone of Vibrio cholerae and its relationship to other pandemic and epidemic V. cholerae isolates

Examination of 58 Vibrio cholerae epidemiologically unassociated isolates and isolated from patients of different countries from 1931 to 1993 by ribotyping helps analyze the genetic variation and molecular evolution of the seventh-pandemic clone of Vibrio cholerae and its relationship to other pandemic and epidemic V. cholerae isolates. Major differences in ribotypes exist between sixth and pre-seventh-pandemic isolates. O139 Bengal isolates are similar to isolates from the early seventh-pandemic isolates. Majority of seventh-pandemic isolates fall into two groups and O139 strains evolved from seventh-pandemic isolates have changed twice, in the 1970s and in 1992.