Antibodies to the CNA protein and to other regions from the collagen binding domain, including domain CNA19, are provided, and antibodies produced in this manner have been shown to be cross reactive to both Staphylococcus aureus and Staphylococcus epidermidis bacteria and which can thus be used in the prevention and treatment of infections caused by both of these types of bacteria. In addition, medical instruments can be treated using the antibodies of the invention in order to reduce or eliminate the possibility of their becoming infected or further spreading the infection. In particular, the proteins are advantageous because they are cross-reactive and may thus be administered to patients so as to reduce or prevent severe infection by staphylococcal bacteria of more than one species. Antibodies generated in this manner have also been shown to exhibit displacement activity and can thus be utilized advantageously in methods wherein these antibodies will be administered to patients having pre-existing staphylococcal infections because of the ability to displace bacterial proteins from binding sites on the extracellular matrix. Finally, a method of identifying, isolating and utilizing displacing antibodies is also provided.