Identification, isolation, and partial characterization of a novel Streptococcus uberis adhesion molecule (SUAM)

The ability to attach to the host cell surface has been considered an important virulence strategy in many bovine mammary gland pathogens, including Streptococcus uberis. Research conducted in our laboratory lead to the identification of an S. uberis adhesion molecule (SUAM) with affinity for bovine lactoferrin (LF) and delineation of its role in adherence of S. uberis to bovine mammary epithelial cells. Using a selected bacterial surface protein extraction protocol and affinity chromatography, a 112-kDa protein that had a similar molecular mass and the LF affinity as one of the identified S. uberis LBP described by Fang and Oliver in 1999 was found. To further characterize SUAM, the N-terminal amino acid sequence of this protein was elucidated. A protein query versus translated database TBLASTN search of the National Center for Biotechnology (NCBI), non-redundant database, nr, with the LBP N-terminal amino acid sequence showed no significant similarity with previous entries. Antibodies directed against SUAM and a 17 amino acid long N-terminal sequence (pep-SUAM) inhibited adherence to and internalization of S. uberis UT888 into bovine mammary epithelial cells. Data presented suggests that we have discovered a novel bacterial protein involved in the pathogenesis of this economically important mastitis pathogen.