Pathogenesis of infection by clinical and environmental strains of Vibrio vulnificus in iron-dextran-treated mice

Vibrio vulnificus is an opportunistic pathogen that contaminates oysters ha rvested from the Gulf of Mexico. In humans with compromising conditions, es pecially excess levels of iron in plasma and tissues, consumption of contam inated seafood or exposure of wounds to contaminated water can lead to syst emic infection and disfiguring skin infection with extremely high mortality . V. vulnificus-associated diseases are noted for the rapid replication of the bacteria in host tissues, with extensive tissue damage. In this study w e examined the virulence attributes of three virulent clinical strains and three attenuated oyster or seawater isolates in mouse models of systemic di sease. All six V. vulnificus strains caused identical skin lesions in subcu taneously (s.c.) inoculated iron dextran-treated mice in terms of numbers o f recovered CFU and histopathology; however, the inocula required for ident ical frequency and magnitude of infection were at least 350-fold higher for the environmental strains. At lethal doses, all strains caused s.c. skin l esions with extensive edema, necrosis of proximate host cells, vasodilation , and as many as 10(8) CFU/g, especially in perivascular regions. These dat a suggest that the differences between these clinical and environmental str ains may be related to growth in the host or susceptibility to host defense s. In non-iron dextran-treated mice, strains required 10(5)-fold-higher ino cula to cause an identical disease process as with iron dextran treatment. These results demonstrate that s.c. inoculation of iron dextran-treated mic e is a useful model for studying systemic disease caused by V. vulnificus.