Malassezia ecology, pathophysiology, and treatment

Abstract

Malassezia are lipid dependent basidiomycetous yeasts that inhabit the skin and mucosa of humans and other warm-blooded animals, and are a major component of the skin microbiome. They occur as skin commensals, but are also associated with various skin disorders and bloodstream infections. The genus currently comprises 17 species and has recently been assigned its own class, Malasseziomycetes. Importantly, multiple Malassezia species and/or genotypes may cause unique or similar pathologies and vary in their antifungal susceptibility. In addition to culture-based approaches, culture-independent methods have added to our understanding of Malassezia presence and abundance and their relationship to pathogenicity. Moreover, these novel approaches have suggested a much wider-spread presence, including other human body parts and even other ecosystems, but their role in these arenas requires further clarification. With recent successful transformation and genetic engineering of Malassezia, the role of specific genes in pathogenesis can now be studied. We suggest that characterizing the metabolic impact of Malassezia communities rather than species identification is key in elucidation of pathophysiological associations. Finally, the increasing availability of genome sequences may provide key information aiding faster diagnostics, and understanding of the biochemical mechanisms for Malassezia skin adaptation and the design of future drugs.

The role of the skin microbiota in acne pathophysiology

“…Gram‐positive bacteria Staphylococcus epidermidis and C. acnes , and fungal species (predominately Malassezia ) are the predominant residents on human epithelia and in sebaceous follicles. Present in both healthy and diseased skin, their roles as commensals or opportunistic organisms are not yet fully understood . For example, S. epidermidis produces antimicrobial peptides, while C. acnes produces antimicrobial short‐chain fatty acids, both of which function together with the host innate defence mechanisms to maintain skin health and homeostasis .…”

“…However, these microbial species are also found in opportunistic infections, especially S. epidermidis , which is a causative agent of hospital‐acquired infections . Malassezia are also associated with skin disease and even life‐threatening septic infections . Moreover, these microbes exist as interacting three‐dimensional communities and biofilms, which may positively or negatively affect the skin.…”

Antifungal activity of selected Malassezia indolic compounds detected in culture

“…The human skin harbours an array of microbial species and microorganisms with Malassezia yeasts being the principal eukaryotic organisms . This genus currently includes 17 species and in humans has been associated with the development of pityriasis versicolor (PV), dandruff (DF)/seborrhoeic dermatitis (SD) and certain head and neck manifestations of atopic dermatitis . All these common skin conditions are characterised by a variably compromised skin barrier …”

A traditional Chinese remedy points to a natural skin habitat: indirubin (indigo naturalis) for psoriasis and the Malassezia metabolome

“…Dear Editor , We read with extreme interest the evidence for the dose‐related efficacy of indirubin in plaque psoriasis, which was impressively high and comparable with current systemic therapies . Lin and coauthors appropriately discuss their results, yet we would like to draw attention to a noteworthy aspect of the proposed therapeutic modality: the effectiveness of indirubin highlights the significance of the Malassezia metabolome in psoriasis, a long‐term disputed issue …”

“…Employing systemic antifungals would not be a feasible, selective approach as they would globally limit the entire Malassezia skin populations. Evaluating the chemical arsenal of Malassezia yeasts (indoles and free fatty acids) would lead to more relevant understanding of the impact of this yeast in the development, maintenance and healing of psoriasis plaques.…”