Abstract
Psoriasis is a chronic inflammatory skin disease, whose pathogenesis involves dysregulated interplay among immune cells, keratinocytes and environmental triggers, including microbiota. Bacterial and fungal dysbiosis has been recently associated with several chronic immune-mediated diseases including psoriasis. In this comprehensive study, we investigated how different sampling sites and methods reflect the uncovered skin microbiota composition. After establishing the most suitable approach, we further examined correlations between bacteria and fungi on the psoriatic skin. We compared microbiota composition determined in the same sample by sequencing two distinct hypervariable regions of the 16S rRNA gene. We showed that using the V3V4 region led to higher species richness and evenness than using the V1V2 region. In particular, genera, such as Staphylococcus and Micrococcus were more abundant when using the V3V4 region, while Planococcaceae, on the other hand, were detected only by the V1V2 region. We performed a detailed analysis of skin microbiota composition of psoriatic lesions, unaffected psoriatic skin, and healthy control skin from the back and elbow. Only a few discriminative features were uncovered, mostly specific for the sampling site or method (swab, scraping, or biopsy). Swabs from psoriatic lesions on the back and the elbow were associated with increased abundance of Brevibacterium and Kocuria palustris and Gordonia, respectively. In the same samples from psoriatic lesions, we found a significantly higher abundance of the fungus Malassezia restricta on the back, while Malassezia sympodialis dominated the elbow mycobiota. In psoriatic elbow skin, we found significant correlation between occurrence of Kocuria, Lactobacillus, and Streptococcus with Saccharomyces, which was not observed in healthy skin. For the first time, we showed here a psoriasis-specific correlation between fungal and bacterial species, suggesting a link between competition for niche occupancy and psoriasis. However, it still remains to be elucidated whether observed microbial shift and specific inter-kingdom relationship pattern are of primary etiological significance or secondary to the disease.
Highlights
The skin is our major interface with the outside environment
To point out differences in observed bacterial diversity caused by sequencing of different 16S rRNA variable regions, we sequenced the V1V2 and V3V4 regions in skin samples from psoriatic patients and healthy controls
principal coordinate analysis (PCoA) of unweighted UniFrac distances revealed a significant difference in beta diversity between the V1V2 and V3V4 regions (p ≤ 0.001) (Figure 1B)
Summary
The skin is our major interface with the outside environment It harbors diverse site-specific microbial communities consisting of bacteria, fungi, and viruses (Grice and Segre, 2011). Microbial dysbiosis could cause or exacerbate skin diseases (Cogen et al, 2008; Gallo and Nakatsuji, 2011; Grice and Segre, 2011). Psoriasis is a chronic inflammatory skin disease that involves a dysregulated interplay among immune cells, keratinocytes and environmental triggers, including microbiota (Nestle et al, 2009). Psoriasis is perceived as a complex systemic immune mediated disease or syndrome, significantly associated with many chronic diseases including arthritis, heart disease, diabetes, metabolic syndrome, inflammatory bowel disease (IBD), or celiac disease (Sundarrajan and Arumugam, 2016; Singh et al, 2017). Changes in microbiota composition could be a one of the factors that leads to disruption of intestinal barrier function in psoriatic patients (Mattozzi et al, 2012; Yan et al, 2017)
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