Gut dysbiosis in ankylosing spondylitis is associated with increased fecal calprotectin

• Introduction/Aims: Intestinal dysbiosis may be involved in the pathogenesis of ankylosing spondylitis (AS). We aimed to define differences in the gut microbiota composition between patients with AS, ulcerative colitis (UC) and healthy controls (HC) and determine the relations between gut microbiota, fecal calprotectin (FCal) and disease related variables in AS.Methods: Fecal microbiota was analyzed in patients with AS(N=150), UC(N=18) and HC(N=17) using 16S rRNA sequence technique in a targeted approach. Fecal bacterial abundance and profile was also compared with a healthy reference group creating a Dysbiosis Index score (DI 1-5). The AS patients were assessed with questionnaires, back-mobility tests, FCal, ESR and CRP.Results: Principal component analysis showed highly separate clustering of the microbiota in stool samples from patients with AS, UC and HC. We found an expansion of Proteobacteria and a contraction of Bacteroidetes and Lachnospiraceae in AS. Dysbiosis (defined as DI≥3) was found in 88% of AS and an elevated DI correlated with increased FCal (rS=0.303; p<0.001). Samples from AS patients with FCal<50 (n=57) and >200 mg/kg (n=36) clustered separately in multivariate analysis. The patients with a FCal>200 mg/kg had lower abundance of bacteria with anti-inflammatory effects such as Faecalibacterium prausnitzii and Clostridium and higher abundance of various types of Streptococci. No clear association was found between the overall fecal microbiota composition and HLAB-27 status, disease activity, function or medication.Conclusions: The fecal microbiota signature differed greatly between patients with AS, UC and HC. An increased FCal, suggestive of intestinal inflammation, was associated with aberrations in the microbiota composition and increased dysbiosis.

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MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Reumatologi och inflammation (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine -- Rheumatology and Autoimmunity (hsv//eng)

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