Short Communication: Antifungal susceptibility of Malassezia pachydermatis isolated from the external auditive conduct from dogs, in central Chile

Abstract

Background: External otitis is common in dogs, and one of the main agents involved is Malassezia pachydermatis, a yeast belonging to the otic microbiota. Empirical treatment can fail; therefore, it is essential to know the antifungal susceptibility profile to prescribe appropriate treatment, a fact scarcely reported in Chile.
Aim: This study aimed to determine the antifungal sensitivity of M. pachydermatis isolated from the external auditory canal of dogs in central Chile.
Methods: Ear swabs from 30 dogs (15 healthy and 15 with external otitis) were used. Samples were subjected to cytology and fungal culture. The antifungal susceptibility was determined according to clinical and laboratory standards institute (CLSI) document M44A-2 using the disk diffusion test from amphotericin B, Caspofungin, fluconazole, nystatin, clotrimazole, and voriconazole were used.
Results: The prevalence of M. pachydermatis was 66.7% from 8 healthy dogs and 12 with otitis. While fungal culture was not associated with the patient's clinical condition (p = 0.24), the yeast count by cytology was significantly higher in dogs with otitis (p = 0.003). The strains were sensitive to all antifungals except for Caspofungin, where 55% of the strains were resistant.
Conclusion: Malassezia pachydermatis is isolated more frequently in dogs with otitis, and the ear cytological examination is useful to differentiate colonized dogs versus dogs with otitis. In addition, most antifungals in vitro are active against this yeast, except Caspofungin, an antifungal used in human medicine. This situation should be further
monitored in epidemiological programs to evaluate the possible impact on Chilean public health.