Similar Depletion of Protective Faecalibacterium prausnitzii in Psoriasis and Inflammatory Bowel Disease, but not in Hidradenitis Suppurativa

Background and Aims: Psoriasis and hidradenitis suppurativa [HS] co-occur more often with inflammatory bowel disease [IBD] than expected, due to shared pathogenic and genetic features. It is known that IBD patients harbour an altered intestinal microbiome characterised by a depletion of Faecalibacterium prausnitzii and increase of Escherichia coli. At present, it is unclear whether a similar intestinal microbiome trend can be identified in IBD-associated skin disorders. We therefore investigated the F. prausnitzii and E. coli abundance in psoriasis and HS, with and without concomitant IBD. Methods: Using quantitative polymerase chain reaction, we compared the F. prausnitzii and E. coli abundances in faecal samples from healthy controls [n = 33] with samples from patients with psoriasis [n = 29], IBD [n = 31], and concomitant IBD and psoriasis [n = 13]. Likewise, we analysed samples from patients with HS [n = 17], and concomitant IBD and HS [n = 17]. Results: Psoriasis patients harboured a significantly lower abundance of F. prausnitzii in their stool than healthy controls [p < 0.001], which was similar to IBD patients. Together with the reduced F. prausnitzii levels, the psoriasis patients had a significantly higher abundance of E. coli [p < 0.001]. No significant difference in F. prausnitzii or E. coli abundance was found in HS. It was apparent that patients with concomitant IBD and associated skin disorder had the greatest decrease of F. prausnitzii and increase of E. coli. Conclusions: The study demonstrates, for the first time, an IBD-like decrease of F. prausnitzii together with an increase of E. coli in psoriasis, supporting the presence of a gut-microbiome-skin axis in psoriasis and IBD.