In Vitro Toxicity and Activity of Dakin's Solution, Mafenide Acetate, and Amphotericin B on Filamentous Fungi and Human Cells

Abstract

Posttraumatic invasive fungal infections threaten critically injured combat-related injuries and require a combination of extensive surgery and systemic antifungal therapy, along with topical antimicrobials used adjunctively to control the infection. We evaluated the in vitro activity of topical agents in varying combinations and concentrations against molds from patients that were responsible for wound invasive fungal infections and the topical agents' toxicity to human cells. Mafenide acetate solutions (2.5%, 5%, and 7.5%), amphotericin B solutions (2 µg/mL, 2 mg/mL, and 20 mg/mL), SMAT (5% mafenide acetate in combination with 2 µg/mL, 2 mg/mL, and 20 mg/mL amphotericin B), and Dakin's solutions (buffered sodium hypochlorite) (0.5%, 0.25%, and 0.125% and 10-fold serial dilutions of 0.25%-0.00000025%) were evaluated for antifungal activity against 4 molds using a time-kill assay using standard conidial suspensions of 5 × 10(4) colony-forming units per milliliter. To assess cellular toxicity, confluent monolayers of human keratinocytes, dermal fibroblasts, and osteoblasts were exposed to these topical agents. Based upon efficacy and toxicity ratios, an additional 10 molds were screened with selected concentrations of the topical agents for antifungal activity and toxicity. All the topical agents seemed to have a dose-dependent killing with only mafenide acetate showing time killing associated with prolonged contact. There was overall evidence of dose-dependent cytotoxicity of the various topical agents against the various cell lines tested, but there did not seem to be increased cell death with continued exposure to the agents over time. Dakin's solution exhibited dose-dependent toxicity and efficacy with 0.00025% appearing to optimize those parameters. Mafenide acetate and amphotericin B did not seem to persistently meet the toxicity and efficacy balance as consistently as Dakin's solution.