Molecular epidemiology of Vibrio cholerae in the U.S. Gulf Coast

Enterotoxigenic strains of Vibrio cholerae O-1, biotype El Tor, isolated from a case of cholera in Texas in 1973, an outbreak of cholera in Louisiana in 1978, and Louisiana sewage samples in 1980 and 1981 were analyzed for their genetic similarities. Chromosomal DNA was isolated from each strain, digested with restriction endonuclease, and analyzed by the Southern blot technique. A radioactive probe consisting of Escherichia coli heat-labile enterotoxin DNA detected cholera toxin gene sequences in these strains and demonstrated that the toxin gene sequence, if not the entire chromosomal DNA, is identical in these strains and distinctly different from other strains of V. cholerae isolated throughout the world. In addition, two strains of enterotoxigenic V. cholerae non-O-1 isolated from clinical cases, were analyzed and found to possess cholera toxin genes which differed in the DNA sequence from the V. cholerae O-1 strains. We concluded that a single strain of enterotoxigenic V. cholerae O-1 is resident in the U.S. Gulf Coast and that a second reservoir of cholera toxin genes exists in V. cholerae non-O-1 strains in Louisiana.