Molecular Characterization of the Skin Fungal Microbiota in Patients with Seborrheic Dermatitis

Abstract

Introduction Seborrheic dermatitis (SD) is a common inflammatory skin disorder associated with seborrhea. It is characterized by erythematous patches with yellow-gray scales. These appear most often on the face, especially the nasolabial folds, scalp, and upper trunk, in sebaceous gland-rich areas of the skin. The disorder is present in about 3% of the general population, more prevalent in males than in females, and frequently observed in patients with acquired immunodeficiency syndrome (AIDS) and Parkinson's disease [1,2]. The disease presents in two age groups: newborn infants up to 5 months of age, and young adults with increased sebum secretion from the skin. The human skin is populated by various microorganisms, including bacteria and fungi [3,4]. Of these, skin fungi, Malassezia species, play an important role in the development of SD. As Malassezia species require fatty acids for their growth, they colonize the sebaceous gland-rich areas of the skin, including the face, scalp, and back, where they feed on fatty acids from human sebum. Malassezia species secrete lipases that hydrolyze sebum into triglycerides, which are further hydrolyzed into fatty acids [5-7]. Fatty acids are utilized as nutrition by skin microorganisms, including Malassezia. However, the unsaturated fatty acid oleic acid causes inflammation of the skin directly by eliciting IL-1α secretion from macrophages or epidermal keratinocytes, and is thought to be the causative agent of SD [7]. In fact, the mRNA expression of a specific Malassezia lipase gene can be detected from lesional sites in patients with SD [8,9]. The clinical condition improves on administering antifungal agents, suggesting that Malassezia species are one of the causative agents of SD [10,11]. Tajima et al. [12] analyzed the Malassezia microbiota in the skin of patients with SD using a DNA-based molecular approach. The genus Malassezia currently includes 14 species; of these, M. globosa and M. restricta are the major species in the skin of patients with SD and these species are more abundant at lesional sites than non-lesional sites. In the present study, we analyzed comprehensively the skin fungal microbiota of lesional and non-lesional sites of SD patients to obtain basic information to enable understanding of the development of SD and skin fungal microbiota using a pyrosequencing approach. Abstract Background: Seborrheic dermatitis (SD) is an inflammatory disease associated with seborrhea that appears most often on the face, especially the nasolabial folds, scalp, and upper trunk, in sebaceous gland-rich areas of the skin. Although various factors are involved in the development of SD, Malassezia species of skin fungi play an important role in this skin disease. The aim of this study was to obtain basic information to elucidate the mycological involvement in the development of SD by performing a comprehensive analysis of the skin fungal microbiota of lesional and non-lesional sites in SD patients using a pyrosequencing approach.