Topical antibiotic therapy: current status and future prospects

As we enter a new decade, topical antibiotics are the subject of much renewed interest and are being used on a wider scale than ever before. The reasons for using topical rather than oral therapy for a variety of dermatoses include the reduced risk of systemic side effects, the avoidance of resistance selection in the gut microflora, the higher achievable concentration of antibiotic at the site of action and the overall usage of less drug. Somewhat surprisingly, treatment costs are not reduced by the use of topical therapy. The number of antibiotics licensed for topical use has increased in recent years and now includes representatives of the tetracycline, macrolide, lincosamide, aminoglycoside and peptide families of antibiotics in addition to fusidic acid, chloramphenicol and pseudomonic acid. Opinions regarding the clinical efficacy of topical antibiotics are conflicting, and for most indications alternative oral therapies are available. Topical antibiotics are the drugs of choice for the elimination of nasal carriage of Staphylococcus aureus and for the therapy of eye and external ear infections. They are also effective in the treatment of impetigo and other superficial pyodermas and in the management of localised infected eczema. Topical preparations of erythromycin, clindamycin and tetracycline are widely prescribed for the therapy of acne and are of clinical benefit in mild--moderate cases. However, they are no more effective against inflamed lesions than benzoyl peroxide and are less effective against non-inflamed lesions. They are not as effective as oral tetracycline in moderate to severe acne and should not be considered as a therapy for severe acne, for which 13-cis-retinoic acid is the drug of choice. It is well known that many antibiotics, when used topically, especially for prolonged periods, select for antibiotic-resistant staphylococci at the skin surface. Tetracyclines, erythromycin and clindamycin also select for resistant staphylococci on the surface of intact skin when delivered by the oral route. The contribution of topical antibiotic usage to the current high level of antibiotic resistance in coagulase-negative staphylococci, which are increasingly implicated in infections of compromised hosts, has not been quantified, although it is known that cutaneous staphylococci possess a large pool of transferable resistance genes.(ABSTRACT TRUNCATED AT 400 WORDS)