Proliferation of a bovine mammary epithelial cell line in the presence of bacterial virulence factors.

Effects of bacterial virulence factors on bovine mammary cell structure and function are not well defined. In this study, we evaluated the influence of specific bacterial virulence factors on proliferation of a bovine mammary epithelial cell line. The MAC-T cells were cultured in the presence of medium only, Staphylococcus aureus alpha-toxin, Staph. aureus beta-toxin, Escherichia coli endotoxin, Streptococcus uberis capsule, or hyaluronidase. Cells were cultured in the presence of virulence factors for 48 h at 37 degrees C. The MAC-T cell proliferation was inhibited by all concentrations of endotoxin and alpha-toxin and by most concentrations of hyaluronic acid capsule and hyaluronidase > 7.8 micrograms/ml. Staphylococcus aureus beta-toxin had no effect on MAC-T cell proliferation. Virulence factors produced by mastitis pathogens may influence mammary epithelial cell proliferation in vivo, which could be important during the periparturient period, when mammary tissue undergoes rapid differentiation and growth.