A composition and method useful in promoting healing of a bleeding wound site. The composition preferably includes a substantially anhydrous acid form of a cation exchange resin, which when applied over blood, provides an antimicrobial against planktonic microorganisms and biofilms in the wound. The resin is also capable, when applied in sufficient quantities, of providing a continuing and persistent antimicrobial against planktonic microorganisms and biofilms through dehydration and ion exchange with cations present in the blood and other body fluids. When the resin has a concentration of at least 26 mg/ml, it provides a >3 log reduction in biological activity of MRSA, MRSE and Pseudomonas aeruginosa.