The Incidence of Vibrio Species in Louisiana and Maryland Oysters (Crassostrea Virginica).

Vibrio species, normal inhabitants of the sea and of shellfish harvested from marine or brackish waters, have been established as the causative agents of serious human infections. An investigation to isolate and identity Vibrio species in oysters collected from eight Louisiana commercial oyster beds was conducted. A selection of 127 vibrio isolates and 46 reference strains, including all known Vibrio species, were subjected to a bacteriological identification scheme of 46 parameters. When the data from the wild strains and the reference strains were analyzed by the numerical taxonomy program, TAXAN Version 3.0, six major phena were evident. Four of the phena contained Vibrio parahaemolyticus, Vibrio vulnificus, Vibrio cholerae, Vibrio mimicus, Vibrio furnissii, and Vibrio Group 521. Genetic relatedness studies showed one of the other phena to be composed of isolates of Vibrio damsela. The remaining major phenon appears to be a previously undescribed Vibrio group. Because of the severity and rapidity of the disease process in Vibrio vulnificus infections and because of the high mortality rates associated with these infections, a rapid serological method for V. vulnificus identification was developed. Species-specific anti-V. vulnificus flagellar (H) monoclonal antibody coagglutination reagents were sent to laboratories throughout the United States and Canada to be assessed for specificity. One of the user laboratories reported that fifteen Vibrio strains, isolated from Eastern seaboard oysters, agglutinated in these reagents but did not conform to established V. vulnificus bacteriological profiles. These findings suggested that the reagents may not be species-specific. DNA from representative oyster isolates which produced agglutination reactions were examined for thermal denaturation midpoint temperature, mol% G + C content, and DNA-DNA reassociation with DNA from V. vulnificus biogroups 1 and 2. High percentages of relative reassociation with V. vulnificus reference strains indicate that the H coagglutination reagents exhibit a high degree of specificity for V. vulnificus isolates, even those showing aberrant phenotypic characteristics.