Shared occurrence of Malassezia spp. in dogs and their owners

Malassezia spp. are commensal yeasts inhabiting the skin of humans and animals; however, some species may cause dermatological disorders or bloodstream infections, especially in immunocompromised patients. The fastidious culture requirements of lipid-dependent species hamper understanding of the zoonotic role of this genus. This study investigated the occurrence, fungal load, and epidemiological links of Malassezia spp. between 73 dogs and their owners, comparing sampling methods (i.e., sterile dry swabs vs sterile gauzes) and culture media (i.e., Dixon's agar vs FastFung agar). Samples were collected from dogs and owner in sites exposed to contact (i.e., ears, muzzle, and perianal area in dogs; palms and interdigital spaces in humans). Yeasts were identified using morphological, biochemical, and molecular techniques, and quantified as colony forming units (CFUs). Overall, Malassezia spp. were detected in 68.5% of dogs (n = 50/73) and 21.9% of owners (n = 16/73). Among dog isolates, 49 were identified as Malassezia pachydermatis and one as Malassezia sympodialis; all human isolates were M. pachydermatis. Fungal loads were higher in muzzle than auricular samples (p = 0.017) and on FastFung agar compared with Dixon's agar (p = 0.011), with no significant difference between sampling methods (p = 0.341). Dog and owner fungal loads showed a moderate correlation (ρ = 0.480, p < 0.001), and dog positivity increased the odds of owner colonization (p = 0.044). Phylogenetic analysis of the intergenic spacer 1 (IGS-1) region showed that isolates from dogs and their owners clustered within M. pachydermatis reference sequences, with several dog–owner pairs consistently grouping in the same subclades. The findings underscore the importance of optimized diagnostic protocols for Malassezia spp. infection and suggest the muzzle as a high-risk area for potential zoonotic transmission, with implications for veterinary and public health concern.