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

Abstract

Environmental and clinical Vibrio cholerae 0-1 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 0-1 strains examined in this study, including the tox+ and tox-isolates.

Cholera

“…One interesting application of bacteriophage typing is the use of lysogenic phage as DNA hybridization probes to distinguish strains on the basis of chromosomal integration sites. This technique was used to confirm other studies showing that the U.S. Gulf Coast isolates are clonal and furthermore showed that some nontoxi-genic strains from the Gulf Coast are highly related to the toxigenic strains isolated from patients in this area (144).…”

Molecular cloning of the hemolysin determinant from Vibrio cholerae El Tor

“…These results demonstrate that the Hly-phenotype of the classical V. cholerae strains tested as well as RV79 (Hly-) is not due to a detectable DNA alteration of 200 bp within the hemolysin-encoding region. The results obtained from the Southern blot analysis of SG23, a nonreverting Hly-isolate obtained after mutator vibriophage VcA-3 infection of strain HK-1 (9), demonstrate that the Hly determinant is the hly locus. One would anticipate that VcA-3 integration in, or near, the hly locus should result in insertional inactivation and, in addition, either change the electrophoretic mobility of the single hybridizing fragment in BstEII digests of HK-1 DNA or, alternatively, split the hybridizing fragment into two new segments.…”

“…Mapping of the V. cholerae hly locus. We have previously shown that the mutator vibriophages VcA-1 and VcA-3 are closely related and share considerable sequence homology (9). The presence of a VcA-3 prophage in or near the hly locus of strain HK-1 in SG23 provided a region of homology for VcA-1-mediated transfer (15) from the hly region of the V. cholerae SG54 chromosome into a number of auxotrophic El Tor recipient strains.…”

Phages InfectingVibrio vulnificusAre Abundant and Diverse in Oysters (Crassostrea virginica) Collected from the Gulf of Mexico

“…Unlike most of the phage isolates, which had relatively narrow host ranges and caused lysis only of the strain on which they were originally isolated, some of the phages belonging to the newly described group lysed all five of the host strains as well as all clinical isolates of V. vulnificus tested thus far (data not shown). That many of the phages have a relatively narrow host range suggests that they may be useful in developing a phage-typing system for V. vulnificus, such as has been used for epidemiological studies of related pathogens including V. cholerae (3,9,15). Indeed, susceptibility patterns of V. vulnificus strains to the phage isolates listed in Table 1 clearly distinguished among the five host strains of V. vulnificus.…”