Malassezia pachydermatis is a yeast pathogen associated with recurrent skin and ear infections in dogs, often complicated by biofilm formation and reduced antifungal susceptibility. We aimed to evaluate the in vitro antifungal activity of essential oils and nanoemulsions of Zingiber cassumunar and Cymbopogon citratus compared with conventional antifungal agents against planktonic and biofilm forms of M. pachydermatis. Preliminary screening of six plant extracts was performed using 12 clinical isolates identified Z. cassumunar and C. citratus for nanoemulsion formulation. Antifungal susceptibility testing of conventional antifungal agents and nanoemulsions was subsequently conducted using 31 clinical isolates, and nanoemulsions were prepared by high-pressure homogenization. Both essential oils exhibited antifungal activity, and nanoemulsion formulations showed enhanced inhibitory effects compared with the crude oils. Biofilm-associated cells demonstrated reduced susceptibility, particularly to conventional antifungal agents. Terbinafine was the most potent agent against planktonic cells but showed reduced efficacy in biofilms. Nanoemulsions of Z. cassumunar and C. citratus exhibited improved activity against both forms. These findings suggest that nanoemulsification may enhance the in vitro antifungal performance of essential oils against M. pachydermatis biofilms. However, further studies, including mechanistic investigations and in vivo evaluations, are required to confirm their therapeutic potential and safety.
Promcham et al. (2026) studied this question.