In Vitro Antifungal Activity of Octenidine Against Emerging Dermatophyte Species

Dermatophytes cause a wide range of superficial infections of the skin, hair and nails, with high global prevalence and considerable public health relevance. Treatment regimens for dermatophytosis are limited to few antifungal drug classes, and rising resistance-particularly to terbinafine-further compromises therapeutic efficacy. Topical antiseptics such as octenidine (OCT) may represent a promising option for infection control and local therapy. This study investigated the in vitro antifungal activity of the pure antiseptic OCT (at final assay concentrations of 0.1% and 0.05%) and two OCT-based commercial ready-to-use medicinal products (octeniderm® and octenisept®) against clinical isolates of emerging (drug-resistant) dermatophytes including Trichophyton rubrum, T. mentagrophytes, T. tonsurans, T. interdigitale, T. indotineae and Microsporum canis. Quantitative suspension assays were conducted according to EN 13624:2013 under low organic load (0.3 g/L bovine serum albumin) and high organic load (3 g/L bovine serum albumin, 3 mL/L defibrinated sheep blood), with contact times ranging from 1 to 15 min. Results showed that the active OCT itself as well as the skin antiseptic octeniderm® and the wound and mucous membrane antiseptic octenisept® are effective against the tested dermatophytes in a time- and concentration-dependent manner. Notably, octeniderm® was able to inhibit fungal growth within 1 min, even under high organic load conditions. These in vitro findings suggest that OCT, a well-tolerated antiseptic already in clinical use represents a potential option for preventing transmission and managing superficial infections caused by (drug-resistant) dermatophytes.