Antimicrobial Activity of Iodoquinol 1%–Hydrocortisone Acetate 2% Gel Against Ciclopirox and Clotrimazole

Commercially available topical formulations consisting of iodoquinol 1%–hydrocortisone acetate 2%, ciclopirox 0.77%, and clotrimazole 1%–betamethasone dipropionate 0.5% were assessed for their antimicrobial activity against cultures of Micrococcus luteus, Propionibacterium acnes, methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, Corynebacterium aquaticum, Trichophyton mentagrophytes, Malassezia furfur, Microsporum canis, Candida albicans, Trichophyton rubrum, or Epidermophyton floccosum. At 1 and 5 minutes following inoculation into suspensions of each product, aliquots were removed, serially diluted, and plated onto appropriate agar to determine the log reduction in colony-forming units (CFUs) for each organism. Iodoquinol 1% produced the broadest and greatest antimicrobial activity as measured by a 3-log reduction of CFU, active against all microbes tested following incubation times of 1 or 5 minutes, except M luteus. By contrast, ciclopirox 0.77% and clotrimazole 1% showed activity against P aeruginosa and T rubrum, with ciclopirox also killing M luteus, P acnes, M canis, C albicans, and E floccosum at 5 minutes. Iodoquinol 1%–hydrocortisone acetate 2% also was the only product that showed effective antibacterial reduction of MRSA at 1 minute.