Characterization of mechanisms involved in uptake of Streptococcus dysgalactiae by bovine mammary epithelial cells.

Bovine mammary epithelial cells were pretreated with inhibitors of protein kinase activity, actin polymerization and receptor-mediated endocytosis. In addition, mammary epithelial cells and Streptococcus dysgalactiae were pretreated with inhibitors of protein synthesis. Results showed that activity of tyrosine protein kinases, intact microfilaments and de novo eukaryotic protein synthesis was required for uptake of S. dysgalactiae by bovine mammary epithelial cells; a process that appeared to occur via receptor-mediated endocytosis. In contrast, de novo bacterial protein synthesis was not required for uptake of S. dysgalactiae by MAC-T cells. This study provides insight into bacterial and cellular mechanisms involved in early host-pathogen interactions, putting into perspective the role of mammary epithelial cells in the development and establishment of intramammary infections by S. dysgalactiae.