THE EMERGING DIVERSITY OF THE ELECTROPHORETIC TYPES OF VIBRIO-CHOLERAE IN THE WESTERN-HEMISPHERE

Since the Latin American cholera epidemic began in 1991, 447 isolates of Vibrio cholerae O1 from the Western Hemisphere have been assayed by multilocus enzyme electrophoresis (MEE) to determine allelic variatio n among 16 enzyme-encoding genes. Two electrophoretic types (ETs) were identified among toxigenic isolates from Latin America: 323 were ET 4 , the ET associated with the Latin American epidemic, and 29 were ET 3 . Twenty-three of these ET 3 isolates had a distinctive antimicrobial resistance pattern also seen in isolates imported into the United Stat es from Latin America and Southeast Asia. These resistant isolates had an identical ribotype and nearly identical pulsed-held gel electropho resis (PFGE) patterns. Most nontoxigenic isolates analyzed were not pr ecursors or descendants of toxigenic epidemic strains. MEE provided a population genetic framework for the interpretation of PFGE and riboty pe data from the isolates in this study. All three methods identified 2 distinct strains of toxigenic V. cholerae O1 currently epidemic in L atin America.