VIBRIO PARAHAEMOLYTICUS: INFECTION OR TOXICOSIS?1

The facultative halophile Vibrio parahaemolyticus, since its first isolation, has been shown to be toxic for mice and has produced experimental infection when fed to animals and humans. Pathogenicity has been shown to be associated with the presence of a heat-stable hemolysin-the Kanagawa-hemolysin. Previously, investigators reported that most strains of V. parahaemolyticus, regardless of virulence, could produce dilatation in the ligated rabbit gut. We have shown however, that ileal loop reactivity is strongly associated with Kanagawa-hemolysin and, thus, with virulence. Reactivity is obtained with live cell suspensions and the reaction time is dose dependent. Other investigators have reported that preparations of heated cells, cell lysates, culture filtrates, and purified Kanagawa-hemolysin will not produce dilatation in rabbit ileum nor edema in the mouse foot pad. In our studies, cell-free culture filtrates were without effect in the ligated ileal loop, suggesting absence of enterotoxin. Cell wall and heated cell preparations yielded varying ileal reactions. Present data are insufficient to describe the mechanism of virulence of V. parahaemolyticus.