Azole and terbinafine susceptibility testing of Malassezia pachydermatis in Japan

Canine Malassezia dermatitis and otitis externa are generally treated by antifungal drugs. However, multi-drug-resistant strains of Malassezia pachydermatis have been reported worldwide. Given the presence of these multi-drug-resistant strains, it is unclear which antifungal agent is the most effective for canine Malassezia dermatitis and canine otitis. In this study, we attempted to determine the most effective drug against azole-resistant M. pachydermatis. Susceptibility to azoles and terbinafine (TBF) was assessed using a modified broth microdilution method. In all tested isolates, the minimum inhibitory concentration at 90% of organisms (MIC₉₀) were 16 to >32 μg/mL for the azoles, and 2 μg/mL for TBF. All of the strains that showed low susceptibility to both itraconazole and miconazole were also relatively susceptible to TBF.