ENTEROTOXIC ACTIVITY OF HEMOLYSIN BL FROM BACILLUS-CEREUS

Bacillus cereus causes exotoxin-mediated diarrheal food poisoning. Hemolysin BL (HBL) is a well-characterized B. cereus toxin composed of three components (B, L(1), and L(2)) that together possess hemolytic, cytotoxic, dermonecrotic, and vascular permeability activities. Here, we show that HBL causes fluid accumulation in ligated rabbit peal loops at a dose of 5 mu g of each component per loop. Maximal fluid responses occurred for combinations of all three components at greater than or equal to 25 mu g of each component per loop. Individual components and binary combinations did not cause significant fluid accumulation at 25 mu g of each component. Specific antisera to HBL components inhibited the fluid accumulation response of crude culture supernatant from B. cereus F837/76. These antisera were tested against an antiserum to a partially characterized multicomponent diarrheal toxin described previously by Thompson et al. (N. E. Thompson, M. J. Ketterhagen, M. S. Bergdoll, and E. J. Shantz, Infect. Immun. 43:887-894, 1984). Immunoblot and immunoprecipitation analyses indicate that HBL and that toxin are identical. These results confirm previous speculation that HBL is a tripartite entertoxin that, as for all of its other known activities, requires all three components for maximal activity.