Rapid Molecular Detection of Antifungal-Resistant Strains of Malassezia pachydermatis.

Azole resistance in Malassezia pachydermatis has been reported in isolates from canine skin worldwide. Decreased susceptibility of M. pachydermatis to azoles has been hypothesized to potentially result from mutations in the ERG11 gene, which encodes lanosterol 14α-demethylase. To sequence the mutation hotspots of ERG11 in the isolates, we prepared primers (MPERG11hot2S and MPERG11hot2R) based on the conserved sequences of M. pachydermatis ERG11. DNA samples from azole-resistant and -susceptible strains were amplified by PCR using the primer pair. PCR amplicons were sequenced and analyzed for single-nucleotide polymorphisms (SNPs) in the target gene. Seven of the tested azole-resistant strains (16 strains) harbored ERG11 SNPs at nucleotide 904 (G→A) or 905 (C→T), resulting in the replacement of Ala 302 with Thr or Val (Ala302Thr or Val). None of the tested azole-susceptible strains had a mutation at either of those residues. Our PCR method detected SNPs at the nucleotide-905 (C→T) hotspot mutation site in M. pachydermatis ERG11. Moreover, we discovered an additional hot spot site at nucleotide 904 (G→A).