First description of antifungal susceptibility of yeast-like fungi in dermal lesions of dogs in Portugal: A 6-year pilot retrospective study (2018-2023)

Abstract

Yeast infections, particularly those caused by species of the genera Malassezia and Candida, are important contributors to otitis and dermatitis in dogs. This study investigates the prevalence and antifungal resistance of various yeast-like fungi isolated from canine dermal lesions in Portugal. Between 2018 and 2023, samples from dogs with clinically suspected yeast infections were collected and analysed using the Vitek 2 Compact® (bioMérieux, Marcy-l'Étoile, France) and FUNGITEST™ 60780 kit (Bio-Rad, Hercules, USA). A total of 24 fungal isolates were identified, including Malassezia pachydermatis and Candida albicans. Susceptibility testing revealed high sensitivity to antifungal agents such as fluconazole, ketoconazole, itraconazole, and miconazole across most species, with notable resistance observed in Rhodotorula mucilaginosa to multiple antifungals. Intermediate resistance levels were detected in Malassezia spp. to flucytosine and several other antifungals. These findings underscore the need for continuous monitoring and prudent antifungal use to prevent resistance development. The study also highlights the importance of revisiting treatment protocols for Malassezia infections in dogs, given the observed resistance patterns. Further research is recommended to explore the genetic and molecular mechanisms underlying antifungal resistance and develop new therapeutic agents.