Dysbiosis of the Saliva Microbiota in Patients with Psoriasis: A Case-Control Study

Accumulating evidence supports the association between altered salivary microbiota and inflammatory diseases. The existing literature on the salivary microbiota in patients with psoriasis is limited. However, differences in the prevalence of Candida species and abundance of several bacterial taxa in saliva have been found between patients and controls. This study aimed to investigate the differences in the composition and functional potential of salivary microbiota in patients with psoriasis compared to their cohabiting partners and healthy controls.

Samples from 115 of 123 individuals qualified for statistical analysis: patients with psoriasis who did not receive systemic anti-psoriatic treatment (n=47); cohabiting partners (n=21); and age-, sex-, and BMI-matched healthy controls (n=47). One saliva sample was collected from each participant and analysed by shotgun metagenomic sequencing.

A difference in the α-diversity of bacterial species was observed exclusively between patients and controls, with a lower diversity in patients (p=0.041). Variation in bacterial composition (β-diversity) was influenced by smoking (p=0.001) and diet (p=0.025) but not by group status. Using a linear regression model adjusted for smoking and diet, we identified four bacterial classes and five species that were significantly different between the patient, partner, and control groups. One Kyoto Encyclopedia of Genes and Genomes module differed significantly between patients with psoriasis and their partners. No differences in Candida species or abundance were found among the three groups.

Comparison of salivary microbiota at the levels of bacterial diversity, composition, and predicted function indicated that psoriasis cases are characterised by dysbiosis.