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Vibrio cholerae, recognized as the causative agent of epidemic cholera, was isolated from healthy professional divers and from water samples collected at dive sites in the United States, Ukraine and Russia. Swabs of nose, ear and throat of divers and their tank regulators, i.e. the divers and their diving gear, were taken before and after routine dives. Blood samples were collected before and 30-60 days after each dive to measure IgG and IgA titers against the whole cell antigen of V. cholerae O1. Nine strains of V. cholerae O1 and nine strains of V. cholerae non-O1 were isolated during this study. These isolates were identified by conventional biochemical tests and indirect fluorescent antibody staining methods, using fluorescein isothiocyanate-labeled monoclonal antibody, COLTA, prepared against the 'A' antigenic factor of the lipopolysaccharide of V. cholerae O1, and serotyped by slide agglutination. Seven of the nine strains of V. cholerae O1 isolated and successfully cultured during the studies, were toxigenic by enzyme-linked immunosorbent assay and polymerase chain reaction. Analyses of IgG and IgA antibodies of the divers showed that most of the divers had prior exposure to V. cholerae O1. V. cholerae serotype non-O1 strains isolated during the study were found to be non-toxigenic.

Polynucleotide sequence relationships between two reference Vibrio parahaemolyticus strains isolated from Japanese and American gastroenteritis patients were investigated by use of (32)P-DNA/DNA reassociation in free solution. In addition, these strains were similarly compared with 22 other strains of estuarine and marine vibrios, including 11 strains previously identified as V. parahaemolyticus (2 Japanese, 1 of unknown location, and 8 American strains obtained from diverse geographical locations and sources in North America), 3 strains of V. alginolyticus, and 8 of Vibrio spp. Deoxyribonucleic acid (DNA) from the Japanese and American gastroenteritis isolates showed high relative levels of intraspecific duplex formation (92 to 93%) when reassociated, reciprocally, at 60 C. Heterologous DNA duplexes exhibited thermal elution midpoint [Tm(e)] values comparable to those obtained from homologous duplexes (88.0) when thermally eluted from hydroxyapatite, thus indicating high base-pair complementarity. Other V. parahaemolyticus strains showed DNA homologies of 85% or greater, with correspondingly high Tm(e) values (86.0 to 88.0) for the heteroduplexes formed. DNA of two of three V. alginolyticus strains (ATCC 17749 and 166-70) was 55 to 60% homologous to reference V. parahaemolyticus DNA preparations; Vibrio sp. strain 5144 (originally classified as V. parahaemolyticus biotype 2 and subsequently as V. alginolyticus strain 5144) showed only 24 to 26% DNA homology to the same reference DNA. These data provide evidence that Vibrio sp. strain 5144 is genetically distinct from the other V. alginolyticus strains used in this study. Three bioluminescent strains thought to be closely related to V. parahaemolyticus demonstrated only 24 to 31% DNA homology to the reference V. parahaemolyticus DNA. These data firmly establish the existence in some Atlantic and Gulf Coast estuaries of organisms genetically very similar to V. parahaemolyticus, the causative agent of "shirasu" food poisoning in Japan.