Effects of Staphylococcus aureus toxins on the growth of bovine mammary epithelial cells (MAC-T) in culture

The effects of Staphylococcus aureus M60 culture supernatant on growth of mammary epithelial cells were tested in vitro. Exposure of MAC-T cells to S. aureus culture supernatant reduced cell proliferation and colony-forming ability because of reduced ability to adhere to plastic. Growth-inhibiting effects of S. aureus culture supernatant were abolished by pretreatment with trypsin. Lysis of S. aureus cells with lysostaphin demonstrated that the inhibition was also present in cell lysates. Treatment of MAC-T cells with culture supernatant from isogeneic mutants of S. aureus M60 that produced either alpha or beta toxins implicated alpha toxin as the main factor inhibiting cell proliferation