EFFECT OF STAPHYLOCOCCAL BETA-TOXIN ON THE CYTOTOXICITY, PROLIFERATION AND ADHERENCE OF STAPHYLOCOCCUS-AUREUS TO BOVINE MAMMARY EPITHELIAL-CELLS

The effect of staphylococcal beta toxin on the cytotoxicity, prolifera tion and adherence of S. aureus to bovine mammary epithelial cells was studied. Bovine erythrocytes and mammary epithelial cells were incuba ted with purified staphylococcal cu and beta toxins and with culture s upernatants from S. aureus M60 and two mutant strains that are negativ e for either the production of alpha (DU5789(alpha-)) or beta (DU5846( beta-)) toxin. Lysis of bovine erythrocytes was due primarily to beta toxin. Alpha toxin increased the lysis of bovine erythrocytes by purif ied beta toxin, but the presence of ct toxin in culture supernatants f rom S. aureus did not increase the lysis of bovine erythrocytes. Purif ied beta toxin was cytotoxic to mammary secretory epithelial cells, bu t to a lesser extent than a toxin. Together they exhibited an additive effect on mammary epithelial cells. inactivation of the alpha toxin-g ene of S. aureus M60 decreased the cytotoxic effect on mammary epithel ial cells to a greater extent than the inactivation of the beta toxin- gene. Also, the relative percentages of DU5789(alpha-) and DU5846(beta -) adhering to mammary cell monolayers, the number and size of colonie s and the number of infected epithelial cells decreased. This in vitro study showed that beta toxin damages bovine mammary secretory epithel ial cells, increases the damaging effects of a toxin, increases the ad herence of S. aureus to mammary epithelial cells and increases the pro liferation of S. aureus.