Characterization of hemolytic activity of Staphylococcus aureus strains isolated from bovine mastitic milk

Beta (beta) and delta (delta)-hemolysin of Staphylococcus aureus strains we re cultured in vitro in milk lactoserum (whey) prepared from both healthy a nd mastitis bovine milk. Production of beta- and delta -hemolysins were det ected in 12 out of 50 strains studied. The association between N-acetyl-bet a -D-glucosaminidase (NAGase) activity, plasmin activity (PL) and trypsin i nhibitory capacity (TIC), known as inflammatory indicators for mastitis, an d hemolytic activity were also studied. Mastitic milk decreased directly th e lytic effect of both beta -and delta -hemolysins of S. aureus on hemolyti cal blood agar plates. S. aureus in healthy milk samples produced more beta -hemolysin (3 times) and delta -hemolysin (2 times) when compared to S. au reus supernatants in milk from infected quarters. Furthermore, beta- and de lta -hemolysis correlated negatively with TIC and NAGase and PL activities. Addition of reduced glutathione (GSH) or beta -mercaptoethanol into the ar tificial medium enhanced hemolysins activity.