Molecular epidemiological studies of United States Gulf Coast Vibrio cholerae strains: integration site of mutator vibriophage VcA-3.

Environmental and clinical Vibrio cholerae O-1 strains isolated from the U.S. Gulf Coast region were found to be lysogenic for a vibriophage which we have designated VcA-3. Comparison of VcA-3 with the previously described vibriophages VcA-1 and VcA-2 has shown that VcA-1 and VcA-3 are homoimmune, have extensive sequence homology, but have markedly different restriction endonuclease digestion patterns. VcA-3 was found to randomly integrate into the V. cholerae RV79 chromosome and to introduce stable auxotrophic mutations. We show that all U.S. Gulf Coast environmental and clinical isolates that are lysogenic for VcA-3, including both tox+ and tox- isolates, contain the prophage integrated at an identical chromosomal site. Given the known stability of temperate mutator bacteriophages, these results suggest that there is a clonal relationship among the V. cholerae O-1 strains examined in this study, including the tox+ and tox- isolates.