SELENOUREIDO MOLECULES ARE EFFECTIVE INHIBITORS OF MALASSEZIA PACHYDERMATIS FIELD STRAINS FROM DOGS

Malassezia pachydermatis (MP) is responsible of severe cutaneous infections in companion animals -particularly in dogs - causing dermatitis and external otitis, which recently gained attention for its increasing azole resistance. For this reason, reaching novel therapeutic strategies is of great interest. In previous work, compounds bearing acyl/selenoureido moieties and primary/secondary sulfonamide groups acting through organic selenium and Carbonic Anhydrases inhibition were evaluated. Eight of these compounds (5g, 7a, 7c, 7k, 8c, 10c, 11b, 11f) were tested in vitro by MIC assay against 32 field MP. These strains were isolated from dogs affected by dermatitis and/or external otitis in which a yeast etiology was suspected after cytological examination. Each sample was firstly cultured onto Sabouraud agar then isolates were identified by CHROM-agar® Malassezia. Confirmation of the ID was performed with a nested PCR for internal transcribed spacer region of rRNA gene. In comparison each isolate was tested with MIC assay for its susceptibility to ketoconazole (KTZ). In general, the MIC of tested compounds on field MPs were higher than the reference MP (DSMZ 6172). Despite this, compounds 11b, 8c and 7a showed a lower MIC in 8,1,1/32 field strains, respectively. The MIC of KTZ on field strains showed an average value of 0.94 ± 0.14, including three strains whose MIC values were 16, 8 and 5 μg/ml. On these three strains, compounds 7a, 8c and 10c showed lower MIC values, suggesting greater efficacy of selenoureas than KTZ in phenotypically azole-resistant MP. Confirmation of genotypic resistance to azoles will be needed.