Antifungal agent susceptibilities and interpretation of Malassezia pachydermatis and Candida parapsilosis isolated from dogs with and without seborrheic dermatitis skin

Abstract

Malassezia pachydermatis and Candida parapsilosis are recognized as commensal yeasts on the skin of healthy dogs but also causative agents of seborrheic dermatitis, especially in atopic dogs. We determined and compared the susceptibility levels of yeasts isolated from dogs with and without seborrheic dermatitis (SD) using the disk diffusion method (DD) for itraconazole (ITZ), ketoconazole (KTZ), nystatin (NYS), terbinafine (TERB) and 5-fluorocytosine (5-FC) and the broth microdilution method (BMD) for ITZ and KTZ. The reliability between the methods was assessed using an agreement analysis and linear regression. Forty-five M. pachydermatis and 28 C. parapsilosis isolates were identified based on physiological characteristics and an approved molecular analysis. By DD, all tested M. pachydermatis isolates were susceptible to ITZ, KTZ, NYS and TERB but resistant to 5-FC. Only 46- 60% of the tested C. parapsilosis isolates were susceptible to KTZ, TERB and 5-FC, but ITZ and NYS were effective against all. By BMD, over 95% of M. pachydermatis isolates were susceptible to KTZ and ITZ with an MIC90 < 0.03 and 0.12 μg/ml, respectively. The frequency of KTZ- and ITZ-resistant C. parapsilosis was 29% and 7%, and the MIC90 values were 1 μg/ml and 0.5-1 μg/ml, respectively. Regarding the agreement analysis, 2.2% of minor errors were observed in M. pachydermatis and 0.2-1% of very major errors occurred among C. parapsilosis. There were no significant differences in the yeast resistance rates between dogs with and without SD. KTZ and ITZ were still efficacious for M. pachydermatis but a high rate of KTZ resistant was reported in C. parapsilosis. © 2013 ISHAM.