[Characterization of a transpositional mutant of Staphylococcus aureus underproducing exoproteins]

A pleiotropic transpositional mutant derived from Staphylococcus aureus strain RC46, from bovine origin, was isolated and characterized. This mutant showed decreased production of several exoproteins such as alpha- and beta-hemolysins, DNase, coagulase and extracellular protein A. The production of cell-bound protein A, proteases and delta-hemolysin was not affected. The pleiotrophy of this mutant, designated sae (for S. aureus exoprotein expression), is due to a single insertion of transposon Tn917, as indicated by Southern blot hybridization. The sae mutant showed decreased virulence since its LD50 determined by intraperitoneal injection in mice was 32 times higher than that of the parental strain RC46.