Malassezia: Zoonotic Implications, Parallels and Differences in Colonization and Disease in Humans and Animals

Abstract

Malassezia spp. are commensals of the skin, oral/sinonasal cavity, lower respiratory and gastrointestinal tract. Eighteen species have been recovered from humans, other mammals and birds. They can also be isolated from diverse environments, suggesting an evolutionary trajectory of adaption from an ecological niche in plants and soil to the mucocutaneous ecosystem of warm-blooded vertebrates. In humans, dogs and cats, Malassezia-associated dermatological conditions share some commonalities. Otomycosis is common in companion animals but is rare in humans. Systemic infections, which are increasingly reported in humans, have yet to be recognized in animals. Malassezia species have also been identified as pathogenetic contributors to some chronic human diseases. While Malassezia species are host-adapted, some species are zoophilic and can cause fungemia, with outbreaks in neonatal intensive care wards associated with temporary colonization of healthcare worker’s hands from contact with their pets. Although standardization is lacking, susceptibility testing is usually performed using a modified broth microdilution method. Antifungal susceptibility can vary depending on Malassezia species, body location, infection type, disease duration, presence of co-morbidities and immunosuppression. Antifungal resistance mechanisms include biofilm formation, mutations or overexpression of ERG11, overexpression of efflux pumps and gene rearrangements or overexpression in chromosome 4.

Potential Fungal Zoonotic Pathogens in Cetaceans: An Emerging Concern

“…Malassezia species, commonly found as commensals on the skin, in the oral and sinonasal cavities, as well as in the lower respiratory and gastrointestinal tracts, encompass eighteen species that inhabit humans, various mammals, and birds [ 141 , 142 , 143 ]. These species have been recovered from multiple environments, indicating their evolutionary adaptation from an original ecological niche in plants and soil to the mucocutaneous ecosystem of warm-blooded vertebrates [ 141 ]. In both humans and pets like dogs and cats, dermatological conditions associated with Malassezia exhibit certain similarities.…”

“…Systemic infections by Malassezia , increasingly reported in human cases, have not yet been recognized in the animal population. Furthermore, Malassezia species have been identified as contributing factors in certain chronic human diseases [ 141 , 142 , 143 ].…”

“…Some species in the genus, while primarily host-adapted, display zoophilic characteristics and have been implicated in cases of fungemia. Notably, outbreaks in neonatal intensive care units have been linked to healthcare workers’ transient hand colonization after contact with their pets [ 141 , 144 ]. The susceptibility to antifungals can differ based on several factors, including the specific Malassezia species, the location of infection on the body, the type and duration of the infection, the presence of co-morbidities, and the state of the host’s immune system [ 142 , 143 ].…”

Interactions between Malassezia and New Therapeutic Agents in Atopic Dermatitis Affecting Skin Barrier and Inflammation in Recombinant Human Epidermis Model

“…Malassezia species are lipophilic yeasts, mainly colonized in the head and neck areas where skin lipid is rich [ 11 ]. Malassezia is recognized as a pathogen in various skin disorders, including seborrheic dermatitis, pityriasis versicolor, Malassezia folliculitis, and head and neck dermatitis in AD, and psoriasis, in immunologically competent hosts [ 12 , 13 ].…”

“…Malassezia species do not typically cause sensitization in healthy people, but a significant portion of AD patients show increased serum immunoglobulin E to Malassezia [ 15 ]. Among the 14 identified species of Malassezia , M. sympodialis , M. globosa, M. furfur, and M. restricta have been studied with respect to various human skin diseases [ 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ]. M. restricta, M. globosa, and M. sympodialis are the most frequently identified species in AD skin [ 19 ].…”