FC13 Comparative analysis of the oral microbiota in patients with psoriasis, their cohabiting partners, and healthy controls

Abstract Accumulating evidence supports an association between altered oral microbiota and inflammatory diseases. However, the existing literature on the role of the oral microbiota in patients with psoriasis is limited. Previous studies demonstrated conflicting results and have never been based on shotgun metagenomic sequencing. Several differences have been found in taxa abundance between patients and controls, and culture-based studies all found increased levels of Candida species in patients with psoriasis. The objective was to investigate the differences in the composition and the functional potential of the oral microbiota in patients with psoriasis compared with their partners and healthy controls. A case–control study was conducted with 123 participants divided into three groups; patients with psoriasis not receiving systemic anti-psoriatic treatment (n = 52), cohabiting partners of the patients (n = 21), and age-, sex- and body mass index-matched healthy controls (n = 50). One saliva sample was collected from each participant and analysed by shotgun metagenomic sequencing. Statistical analyses included a comparison of α- and β-diversity, as well as an abundance of the different taxa and Kyoto Encyclopedia of Genes and Genomes (KEGG) modules. A total of 115 samples were included in the statistical analysis, divided into patients with psoriasis (n = 47), partners (n = 21) and healthy controls (n = 47). No significant differences in baseline characteristics were found between patients with psoriasis and their partners. Smoking status (P < 0.0001) and physical activity levels (P = 0.0071) differed between the psoriasis and control groups. We observed a significant difference in α-diversity in the oral microbiome between patients with psoriasis and controls (P = 0.014), showing lower diversity in patients with psoriasis. β-Diversity analysis showed shifts in composition due to smoking (P = 0.014), but no other investigated variable had a significant association with the β-diversity, although the psoriasis group tended to cluster together apart from the two control groups. Abundance analysis was performed using both Mann–Whitney U-test and linear regression, with the former method showing one species (Leptotrichia sp018128225, FDR = 0.079) and one family (Leptotrichiaceae, FDR = 0.059) significantly different between patients and controls, whereas the latter method identified two taxa significantly different between psoriasis and control groups, as well as 21 taxa and 1 KEGG module significantly different between the psoriasis group and their partners at an FDR-adjusted P-value cut-off of 0.1. No differences were found in the abundances of Candida species. A comparison of the microbiomes of individuals with psoriasis and controls indicates that psoriasis is associated with changes in oral microbiota diversity, composition and function.