The Skin Mycobiome of Patients With Atopic Dermatitis and Healthy Volunteers: A Case-Control Study.

Atopic dermatitis (AD) is a common inflammatory skin disease, for which dysbiosis of the skin mycobiome is considered a triggering factor. The aim of this study was to explore the skin mycobiome of AD patients and healthy volunteers (HV). The study included 50 AD patients and as many HV. Culture-based species identification involved a battery of conventional phenotypic tests and PCR sequencing of the internal transcribed spacer (ITS) 1 and 2 regions within the rDNA cluster. Culture-independent, metataxonomic sequencing was performed with ITS1 as the target region. The overall culture-positive rate was higher in AD patients than in HV (74% vs 28%). Among the former, Rhodotorula spp. dominated, followed by Candida spp., Malassezia spp. and Naganishia albida. The congruence between PCR sequencing and phenotyping was 68.6%. Upon metataxonomy of AD samples, 33 (66%) demonstrated close clustering with HV samples ('control-like' AD), while 17 (34%) displayed a remarkably different mycobiome composition ('AD-specific'), with Cladosporium, Malassezia, Candida, Diplodia, Saccharomyces, Penicillium and Aspergillus genera showing increased abundance. Patients with 'AD-specific' mycobiomes were more commonly exposed to air-conditioning compared to 'control-like' AD patients (p = 0.030). A subset of patients with AD has a different cutaneous mycobiome make-up dominated by environmental moulds, and Malassezia and Candida yeasts. Anthropogenic factors may affect the cutaneous mycobiome composition in AD and should be taken into account in microbiome studies.