B-161. Role of Toxins in Microvascular Perfusion Deficits Mediated by Clostridium perfringens and Clostridium septicum

M. J. Hickey, R. Y. Q. Kwan, M. M. Awad, C. L. Kennedy, L. Young, L. M. Cordner, D. Lyras, J. J. Emmins, J. I. Rood;
Monash Univ., Clayton, AUSTRALIA.

Clostridium perfringens and Clostridium septicum are the causative agents of gas gangrene (clostridial myonecrosis). Reduced tissue perfusion leading to tissue ischemia is a major factor in the pathogenesis of these syndromes. The C. perfringens alpha-toxin can induce these changes, but its potential synergy with perfringolysin O (theta-toxin) is less well understood. The effect of C. septicum toxins on the microcirculation has not been examined. Therefore, the aim of this study was to use intravital microscopy to examine the effects of C. perfringens and C. septicum toxins on the functional microcirculation, coupled with the use of isogenic toxin mutants to elucidate the role of particular toxins in the resultant microvascular perfusion deficits. This study represents the first time this integrated approach has been used in the analysis of the pathological response to clostridial infections. Culture supernatants from wild-type C. perfringens induced extensive cellular injury within 30 min, as assessed by in vivo uptake of propidium iodide. Furthermore, significant reductions in capillary perfusion were observed within 60 min. Depletion of either platelets or neutrophils reduced the alteration in perfusion, consistent with a role for these blood-borne cells in obstructing perfusion. In addition, mutation of either the alpha-toxin or perfringolysin O structural genes attenuated the reduction in perfusion, a process that was reversed by genetic complementation. C. septicum also induced a marked reduction in perfusion, with the degree of microvascular compromise correlating with the level of the C. septicum alpha-toxin. Together, these data indicate that as a result of its ability to produce alpha-toxin and perfringolysin O C. perfringens rapidly induces cellular injury and a marked reduction in microvascular perfusion. Since C. septicum induces a similar reduction in microvascular perfusion, it is postulated that this function is central to the pathogenesis of clostridial myonecrosis, irrespective of the causative bacterium.