Research Product

Vibrio vulnificus is a naturally occurring marine bacterium that causes invasive disease of immunocompromised humans following consumption of raw oysters. It is a component of the natural microbiota of Gulf Coast estuaries and has been found to inhabit tissues of oysters, Crassostrea virginica (Gmelin, 1791). The interaction of V. vulnificus with oyster host defenses has not been reported in detail. We examined the interaction of V. vulnificus with phagocytic oyster hemocytes as a function of time, temperature, bacterial concentration, pretreatment in hemolymph, and with V. vulnificus translucent and opaque colony morphotypes. Within these experimental parameters, results showed that the association of V. vulnificus with hemocytes increased with time, temperature, and initial V. vulnificus: hemocyte ratio. Pretreatment of V. vulnificus with serum, or increased serum concentration, did not enhance V. vulnificus-hemocyte associations, a result suggesting the absence of opsonic activity. More than 50% of hemocytes bound the translucent, avirulent morphotype, whereas 10% to 20% were associated with the opaque, virulent form, a result indicating that degree of encapsulation was related to resistance to phagocytosis, as previously described for mammalian phagocytes. Understanding these cellular interactions may, in part, explain persistence of V. vulnificus in oyster tissues and its ecology in estuarine environments.