STAPHYLOCOCCUS-AUREUS STIMULATES UROKINASE-TYPE PLASMINOGEN-ACTIVATOREXPRESSION BY BOVINE MAMMARY CELLS

Staphylococcus aureus commonly causes bovine mastitis, but bovine stra ins, unlike human isolates of S. aureus, do not produce the bacterial plasminogen activator, staphylokinase. By use of bovine mammary epithe lial and myoepithelial cell lines, it was found that bovine S. aureus M60 and its culture filtrates induce a 3- to 10-fold increase in uroki nase-type plasminogen activator activity in mammary cell-conditioned m edia and cellular lysates. Furthermore, transcytosis of S. aureus M60 across a mammary epithelial cell monolayer was significantly enhanced by the addition of bovine plasminogen and inhibited by aprotinin. Thes e findings provide evidence that S. aureus M60 can trigger superactiva tion of host plasminogen activator production and may then utilize the plasminogen activator-plasmin(ogen) system to facilitate tissue invas ion without producing staphylokinase.