The invention relates to compositions of a deacetylated poly N-acetylatedglucosamine (dPNAG) of Staphylococci. The dPNAG may be isolated from naturalsources or synthesized de novo.The invention also relates to the use of dPNAGas a vaccine for inducing active immunity to infections caused byStaphylococcus aureus, S. epidermidis, other related coagulase-negative orcoagulase-positive Staphylococci, and other organisms carrying the ica(intracellular adhesion) locus. The invention further provides methods of usefor antibodies directed to dPNAG, particularly for inducing passive immunityto the same class of infections.