The present invention is directed to a monoclonal antibody that binds specifically to a Staphylococcus aureus glucosaminidase and inhibits in vivo growth of S. aureus. Also disclosed are monoclonal antibody binding portions, recombinant or hybridoma cell lines, pharmaceutical compositions containing the monoclonal antibody or binding portions thereof, and methods of treating S. aureus infection and osteomyelitis, and methods for introducing an orthopedic implant into a patient using the monoclonal antibody, binding portion, or pharmaceutical composition of the present invention.