Mupirocin, fusidic acid and bacitracin: activity, action and clinical uses of three topical antibiotics.

Antibiotics applied to the skin must be formulated in a base that is nonirritant and nontoxic. They may have a narrow or fairly wide spectrum of activity but should produce no local reaction or sensitization; the commensal flora should not be affected unduly. Three antibiotics that have been used topically in humans and animals are fusidic acid, mupirocin and bacitracin, all of which have a narrow antibacterial spectrum. When applied to intact skin, fusidic acid penetrates more rapidly than other antibiotics. Clinically, the frequency of staphylococcal resistance to it and to mupirocin has remained low. Fusidic acid and mupirocin have been recommended for the treatment of acute staphylococcal skin lesions. However, the use of topical antibiotics for the treatment of chronic or recurring dermatitis and surgical or infected wounds may be inappropriate because of possible development of resistance and sensitization. Topical use of bacitracin may produce treatment failure and sensitization.