Cytolytic activity and virulence of Vibrio damsela

Abstract

A correlation was observed between the ability of 19 isolates of Vibrio damsela, a halophilic bacterium recently recognized as a human pathogen, to cause disease in mice and to produce large amounts of a cytolytic toxin in vitro. The yield of toxin in the culture supernatant fluids was optimal during the mid- and late-logarithmic phases of growth in medium containing 0.5% Na+ ion, was stable during the stationary growth phase, and was significantly reduced in culture medium containing greater than or equal to 0.8% Na+ ion, even though Na+ ion concentrations ranging from 0.8% to 2% significantly enhanced growth of the bacterium. The activity in toxin preparations partially purified by ammonium sulfate precipitation was deleteriously affected by heat, low and high pH, proteases, dithiothreitol, and chelating agents, but was unaffected by cholesterol, trypan blue, and mixed gangliosides. The toxin had a molecular weight (estimated by gel filtration) of ca. 57,000 and an isoelectric point of ca. 5.7 and was antigenically distinct from previously described cytolysins produced by Vibrio vulnificus, Vibrio parahaemolyticus, and the El Tor biotype of Vibrio cholerae. Bacteriologically sterile, partially purified toxin preparations were lethal for mice after intraperitoneal, intravenous, and subcutaneous administration, and subcutaneous injection elicited grossly observable changes similar to those observed during the lethal experimental infection caused by subcutaneous injection of V. damsela.