Inhibitory effect of terbinafine on the invasion of nails by Trichophyton mentagrophytes.

Abstract

Terbinafine has a broad spectrum of action in vitro and primary fungicidal action against many pathogenic fungi. Its mode of action against dermatophyte fungi in nail keratin is little understood. Our purpose was to determine the bioavailability of terbinafine in a nail fragment model. The effect of terbinafine on adherence and germination of arthroconidia of Trichophyton mentagrophytes on nail fragments was assessed by gross examination and light and electron microscopy. Preexposure of nail fragments to terbinafine concentrations (0.001 to 10 mg/L) inhibited fungal growth and acted as a barrier to dermatophyte invasion. Damaged arthroconidia and distorted hyphae on the surface of nail fragments were observed. This in vitro model provides an alternative system for studying the activity of antifungal agents in nail and demonstrates the morphologic changes in dermatophyte fungi after exposure to terbinafine.