Gut Microbiota Changes in Inflammatory Bowel Diseases and Ankylosing Spondylitis

Background & Aims: Both inflammatory bowel diseases (IBD) and ankylosing spondylitis (AS) can be considered chronic immune disorders sharing common etiopathogenetic mechanisms. Changes in the composition of the intestinal microbiota, which can lead to an abnormal mucosal response, could be the missing link between these two diseases. Our study evaluate the composition of intestinal microbiota and to characterize gut dysbiosis in patients with IBD and AS. Methods: We conducted a prospective case-control study that enrolled 124 patients [20 Crohn's disease (CD), 27 ulcerative colitis (UC), 28 AS, 17 IBD + AS and 32 controls). Intestinal microbiota analysis was performed by real-time polymerase chain reaction in stool samples. Results: The total quantity of bacteria was decreased in all investigated groups compared to the control group. In studied groups, we noticed an increased percentage of Bacteroides and Escherichia coli (E.coli) and a decreased percentage of Clostridium coccoides, Clostridium leptum, and Faecalibacterium prausnitzii compared to the control group. The percentages of Bifidobacterium (p=0.010) as well as Lactobacillus group (p=0.023) were higher in the L3 form of CD patients. In the E2 form of UC, the quantity of Bacteroides was much higher compared to the E3 form (p=0.004). In AS patients, significant correlations were observed only for the Bifidobacterium species, significantly increased in the axial form compared to peripheral disease (p=0.035). Statistically significant correlations were demonstrated between the Crohn Disease Activity Index score and the total bacterial group (p=0.023, r=-0.507), respectively Bacteroides (p=0.021, r=-0.511) and between the Mayo score and Lactobacillus (p=0.001), respectively E. coli (p=0.001). In IBD + AS group, the Crohn Disease Activity Index score was inversely correlated with the total bacterial group (p=0.010) and directly correlated with Lactobacillus (p=0.047). Conclusions: Intestinal dysbiosis is associated with both IBD and AS. In the association of IBD with AS, dysbiosis is intermediate, but it is associated with the more severe articular disease. Bifidobacterium and Lactobacillus (commonly used as probiotics!) were found to be increased in the association between active IBD and active AS. Further studies are needed to understand how dysbiosis regulates the gut immune system and contributes to intestinal and articular inflammation.