CHARACTERIZATION OF A TN925-INDUCED MUTANT OF STAPHYLOCOCCUS-AUREUS ALTERED IN EXOPROTEIN PRODUCTION

An insertional mutant was isolated from a bovine Staphylococcus aureus strain after membrane-mating with a Streptococcus faecalis strain car rying conjugative plasmid pCF10::Tn925. This mutant, designated RC128, showed enhanced production of alpha-hemolysin and proteases and decre ased production of coagulase, extracellular protein A, DNase, lipase a nd delta-hemolysin. No difference was found in the production of beta- hemolysin. Both, Southern blot analysis and transfer of the pleiotropi c mutant phenotype by transduction, indicated that the mutation was or iginated from a single insertion of transposon Tn925. The LD50 determi ned by intraperitoneal administration in mice showed that mutant RC128 was slightly less virulent than its parental strain.