Deletion of sua gene reduces the ability of Streptococcus uberis to adhere to and internalize into bovine mammary epithelial cells

To elucidate the role of Streptococcus uberis adhesion molecule (SUAM) in the pathogenesis of S. uberis mastitis, sua deletion in S. uberis UT888 was achieved by homologous recombination using a thermosensitive plasmid. The deletion mutant was analyzed for sua deletion by PCR, southern blot and DNA sequencing, and was designated Δsua S. uberis UT888. As compared to the isogenic parent strain, Δsua S. uberis UT888 did not produce SUAM based on SDS-PAGE gel and western blot. Deletion of sua and lack of expression of SUAM by Δsua S. uberis UT888 markedly reduced the ability of the sua gene deletion mutant of S. uberis to adhere to and internalize into mammary epithelial cells. These results confirm the central role of SUAM in adherence to and internalization of S. uberis into host cells.