Dysbiosis of the human skin mycobiome in patients receiving systemic IL-23 inhibitors

Alterations of gut microbiota for the onset and treatment of psoriasis: A systematic review

Psoriasis is a chronic, recurrent and systemic inflammatory skin disease which is mediated by immunoreaction. Its pathogenesis is multifactorial, and the exact driving factor remains unclear. Recent studies showed that gut microbiota, which maintain immune homeostasis of our bodies, is closely related with occurrence, development and prognosis of psoriasis. The intestinal microbial abundance and diversity in patients with psoriasis have changed significantly, including intestinal microbiota disorders and reduced production of short chain fatty acids (SCFAs), abnormalities in Firmicutes/Bacteroidetes (F/B), etc. Besides, the intestinal microbiota of psoriasis patients has also changed after treatment of systemic drugs, biologics and small molecule chemical drugs, suggesting that the intestinal microbiota may be a potential response-to-treatment biomarker for evaluating treatment effectiveness. Oral probiotics and prebiotics administration as well as fecal microbial transplantation were also reported to benefit well in psoriasis patients. Additionally, we also discussed the microbial changes from the skin and other organs, which regulated both the onset and treatment of psoriasis together with gut microbiota. Herein, we reviewed recent studies on the psoriasis-related microbiota in an attempt to confidently identify the "core" microbiota of psoriatic patients, understand how microbiota influence psoriasis through the gut-skin axis, and explore potential therapeutic strategies for psoriasis.

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.

The Contribution of the Skin Microbiome to Psoriasis Pathogenesis and Its Implications for Therapeutic Strategies

Psoriasis is a common chronic inflammatory skin disease, associated with significant morbidity and a considerable negative impact on the patients' quality of life. The complex pathogenesis of psoriasis is still incompletely understood. Genetic predisposition, environmental factors like smoking, alcohol consumption, psychological stress, consumption of certain drugs, and mechanical trauma, as well as specific immune dysfunctions, contribute to the onset of the disease. Mounting evidence indicate that skin dysbiosis plays a significant role in the development and exacerbation of psoriasis through loss of immune tolerance to commensal skin flora, an altered balance between Tregs and effector cells, and an excessive Th1 and Th17 polarization. While the implications of skin dysbiosis in psoriasis pathogenesis are only starting to be revealed, the progress in the characterization of the skin microbiome changes in psoriasis patients has opened a whole new avenue of research focusing on the modulation of the skin microbiome as an adjuvant treatment for psoriasis and as part of a long-term plan to prevent disease flares. The skin microbiome may also represent a valuable predictive marker of treatment response and may aid in the selection of the optimal personalized treatment. We present the current knowledge on the skin microbiome changes in psoriasis and the results of the studies that investigated the efficacy of the different skin microbiome modulation strategies in the management of psoriasis, and discuss the complex interaction between the host and skin commensal flora.