Functional similarity between the haemolysins of Escherichia coli and Morganella morganii

Haemolysin produced by a clinical isolate of Morganella morganii was examined for antigenic relatedness to the haemolysin of Escherichia coli and for similarities in mode of action. The M. morganii haemolysin migrated in SDS-PAGE as a single protein band with a slightly higher molecular weight than that of E. coli haemolysin. Several murine monoclonal antibodies against E. coli haemolysin cross-reacted with the M. morganii haemolysin in Western blots. Diminished haemolysis in the presence of osmotically-stabilising solutes indicated the formation of a pore by M. morganii haemolysin with an effective diameter of 1.5-3 nm. Results from dose-response experiments indicated that a single "hit" was sufficient for lysis of an erythrocyte. Detergent solubilisation of toxin-treated membranes led to recovery of bound toxin exclusively in monomeric form. M. morganii haemolysin was a potent leucocidin, that caused rapid leakage of ATP and death of human polymorphonuclear leucocytes. Under in-vitro conditions M. morganii haemolysin displayed similar leucocidal and haemolytic efficiency. The data demonstrate that M. morganii haemolysin shows functional properties virtually identical with those of E. coli haemolysin.