Background: The gut microbiota interacts with the immune system and plays an important role in many inflammatory diseases such as psoriasis, although the exact mechanisms in this disease are not yet well understood.

Objectives: To characterize differences in the microbiota between patients with psoriasis and healthy controls, and to assess the relationship between these differences and the interleukins involved in psoriasis.

Methods: A cross-sectional observational study was conducted in which sociodemographic data, blood samples, and stool samples were collected from patients with psoriasis and healthy controls attending our center between June 2019 and May 2020. Cytokines (interleukin (IL) 17, 22, 23, 31, 33, 36, interferon (IFN) γ, and transforming growth factor (TGF) β) were analyzed using ELISA, and microbiota was analyzed through 16S amplicon sequencing.

Results: Thirty-six patients and 23 controls were included. Absolute abundance analysis found a higher abundance of the phylum Synergistota in the control group (p<0.05). Differential abundance analysis found higher abundance of the genus Subdoligranulum and Lactobacillus, and the species Bacteroides plebeius (p<0.05), and lower abundance of the species Senegalimassilia anaerobia and the genus Ruminococcus (p<0.05) in the psoriasis group. A relationship was observed between Subdoligranulum and TNFα, IL17, IL22, IL23, IL31, IL33, IL36, IFNγ, and TGFβ (p<0.05), as well as between Lactobacillus and IL17, IL23, IL36, TNFα, and TGFβ (p<0.05).

Conclusions: Significant alterations in the gut microbiota of patients with psoriasis were detected and a relationship with inflammatory interleukins, suggesting their involvement in the disease. These findings could aid in the development of future probiotic treatments for psoriasis.