Malassezia: A Commensal, Pathogen, and Mutualist of Human and Animal Skin

Abstract

Identified in the late nineteenth century as a single species residing on human skin, Malassezia is now recognized as a diverse genus comprising 18 species inhabiting not only skin but human gut, hospital environments, and even deep-sea sponges. All cultivated Malassezia species are lipid dependent, having lost genes for lipid synthesis and carbohydrate metabolism. The surging interest in Malassezia results from development of tools to improve sampling, culture, identification, and genetic engineering, which has led to findings implicating it in numerous skin diseases, Crohn disease, and pancreatic cancer. However, it has become clear that Malassezia plays a multifaceted role in human health, with mutualistic activity in atopic dermatitis and a preventive effect against other skin infections due to its potential to compete with skin pathogens such as Candida auris. Improved understanding of complex microbe-microbe and host-microbe interactions will be required to define Malassezia’s role in human and animal health and disease so as to design targeted interventions.

Epidermal barrier dysregulation in atopic skin predisposes for excessive growth of the allergy-associated yeastMalassezia

“…96 No consistent data exist for differential Malassezia colonization levels on human skin. 13,97 Amplicon and metagenomic sequencing studies generally report relative abundances of individual genera or species. Meanwhile, older culture-based studies suffer from the difficulty of cultivating Malassezia spp.…”

“…10 As such, Staphylococci accumulate in AD lesions and produce toxins that exacerbate epidermal inflammation and barrier disruption. 11,12 Another skin microbe that has been tied to AD is Malassezia , 13 although its causal relationship to the disease is less well established. Malassezia is the most abundant fungus in normal human skin and in many warm-blooded animals.…”

“…[15][16][17] Although generally viewed as a commensal, Malassezia is associated with diverse pathological skin conditions, including AD. 13,18 More recently, Malassezia was even connected to extracutaneous pathologies including IBD 19 and cancer. 20,21 In AD, about half of all adult patients, including preferentially those with head-and neck dermatitis, are sensitized to Malassezia.…”

Frequent transitions in mating-type locus chromosomal organization inMalasseziaand early steps in sexual reproduction

“…This adaptation is linked to their lipid-dependent growth, which is associated with the loss of key genes for fatty acid synthesis (4, 5). At present, the genus Malassezia includes 18 species, with M. restricta , M. arunalokei , M. globosa , M. sympodialis , and M. furfur more commonly observed on human skin regardless of health or disease status (6). While these species are often considered commensals, they can also be mutualistic or pathogenic.…”

LiveMalasseziastrains isolated from the mucosa of patients with ulcerative colitis

“…Malassezia is considered the predominant fungus in the human skin. It is a pathobiont involved in various skin diseases, including psoriasis, seborrheic dermatitis, and atopic dermatitis 15 . Studies have indicated a possible role of Malassezia species in chronic diseases occurring at other body sites, such as pancreatic cancer and Alzheimer's disease [16][17][18] .…”