Molecular characterization of Vibrio cholerae 01 strains by pulsed-field gel electrophoresis

Pulsed-field gel electrophoresis (PFGE) was performed on 180 isolates of Vibrio cholerae serogroup 01 representing 6 different multilocus enzyme electrophoresis (MEE) types and 27 rRNA restriction fragment length polymorphism types (ribotypes). Isolates were digested with the restriction enzyme NotI and were separated into 63 patterns on the basis of differences in band arrangements. In general, strains which were different by MEE or ribotyping also had different PFGE patterns. PFGE identified individual strains within a single MEE type or ribotype; isolates with one PFGE pattern were less frequently distinguished by ribotyping. All V. cholerae 01 isolates tested from the Latin American epidemic were indistinguishable by their MEE, ribotype, or PFGE patterns. PFGE could further distinguish strains of this same ribotype isolated in Africa, Europe, the South Pacific, or Southeast Asia. Although both MEE and PFGE could identify the strain from the Latin American epidemic, PFGE was more rapid and less labor intensive. PFGE also distinguished nontoxigenic isolates endemic to the U.S. Gulf Coast from unrelated nontoxigenic isolates. In the present study PFGE was more discriminating than other previously described subtyping assays for V. cholerae 01 and appears to be a useful epidemiologic tool. The seventh pandemic of cholera began in 1961 and spread to much of Asia and Africa within a decade (4). Despite th