Skin Mycobiome of Psoriasis Patients is Retained during Treatment with TNF and IL-17 Inhibitors.

Background: Biological treatment relieves refractory skin lesions in patients with psoriasis; however, changes in the fungal microbiome (the mycobiome) on the skin are unclear. Methods: The skin mycobiome of psoriasis patients treated with TNF inhibitors (TNFi, n = 5) and IL-17 inhibitors (IL-17i, n = 7) was compared with that of patients not receiving systemic therapy (n = 7). Skin swab samples were collected from non-lesional post-auricular areas. Fungal DNA was sequenced by ITS1 metagenomic analysis and taxonomic classification was performed. Results: An average of 37543 reads/sample were analyzed and fungi belonging to 31 genera were detected. The genus Malassezia accounted for >90% of reads in 7/7 samples from the no-therapy group, 4/5 from the TNFi group, and 5/7 from the IL-17i group. Biodiversity was low in those three groups. Few members of the genus trichophyton were detected; the genus Candida was not detected at all. Among the Malassezia species, M. restricta was the major species in 6/7 samples from the no-therapy group, 4/5 from the TNFi group, and 5/7 from the IL-17i group whose the other largest species revealed M. globosa. Conclusions: The mycobiome is retained on post-auricular skin during systemic treatment with TNF and IL-17 inhibitors.