Species-specific hemolysis by Vibrio vulnificus cytolysin

Cytolysin has been incriminated as one of the important virulence determinants in V. vulnificus infection that causes septicemia and serious wound infection. Hemolysis by V. vulnificus cytolysin is colloid-osmotic in nature, and cytolysins after binding to membrane oligomerize to form small pores on erythrocyte membrane. The hemolytic sensitivity by V. vulnificus cytolysin displayed a great variation between the species. Among the species studied, the half lytic doses of cytolysin for sheep, mouse and human erythrocyte suspensions were 0.40, 0.96 and 2.46 hemolytic units, respectively. There was no significant difference between the species in both the binding and pore formation. Under the hypotonic condition, the stability of erythrocytes from sheep, mouse and human was inversely correlated with the hemolytic susceptibility to the cytolysin. Our results indicate that species difference in hemolytic susceptibility to V. vulnificus cytolysin is not dependent on the binding or pore formation, but rather dependent on the unique osmotic stability of erythrocyte membranes, which shows a strong correlation with the size of cells.