Compositions comprising RIP are advantageously formulated in compositions allowing sustained release and protection from degradation, and improved therapeutic efficacy. To that end, RIP compositions may be delivered to the skin or mucosal membranes as a salve or the like. Alternatively or additionally, RIP compositions may be administered in polymeric nanoparticle carriers, which may be biodegradable. Such formulations are compatible with oral administration. The nanoparticle may accommodate a composition comprising a RIP and at least one other antimicrobial agent, e.g., an antibiotic or an antimicrobial peptide. The nanoparticle further may comprise a coating or moiety, such as an antibody or fragment thereof, to assist in cell targeting.