VIABILITY OF VIBRIO-VULNIFICUS IN ASSOCIATION WITH HEMOCYTES OF THE AMERICAN OYSTER (CRASSOSTREA-VIRGINICA)

Certain indigenous estuarine bacteria, such as Vibro vulnificus, may c ause opportunistic human infections after consumption of raw oysters o r exposure of tissues to seawater. V. vulnificus is known to be closel y associated with oyster (Crassostrea virginica) tissues and is not re moved by controlled purification methods, such as UV light-assisted de puration. In fact, when live shellfish are subjected to controlled pur ification, the number of V. vulnificus cells can markedly increase. A review of previous studies showed that few workers have examined mecha nisms in oysters which may influence the persistence of V. vulnificus in shellfish, such as the fate of V. vulnificus following phagocytosis by molluscan hemocytes. The objectives of this study were to define t he intracellular viability and extracellular viability of V. vulnificu s during the phagocytic process and to study the release of specific l ysosomal enzymes. The viability of a virulent estuarine V. vulnificus isolate with opaque morphology was compared with the viability of a tr anslucent, nonvirulent form, the viability of Vibrio cholerae, and the viability of Escherichia coli in phagocytosis experiments. Our result s showed that the levels of phagocytosis and bactericidal degradation of the opaque V. vulnificus isolate were less than the levels of phago cytosis and bactericial degradation of the translucent morphotype. The se findings indicate that encapsulation may contribute to resistance t o ingestion and degradation by hemocytes. The rates of intracellular d eath of V. cholerae and E. coli exceeded the rate of intracellular dea th of the opaque V. vulnificus isolate, even though the ingestion or u ptake rates did not differ significantly. The levels of lysozyme activ ity and acid phosphatase activity were not significantly different in hemocyte monolayers inoculated with V. vulnificus.