P713 Gut microbiota alterations after bowel preparation amongst inflammatory bowel disease patients

Abstract Background Bowel preparation prior to colonoscopy is a routine procedure and supposed to be safe. However, the exacerbation of the complaints could be observed in numerous cases after colonoscopy in patients with inflammatory bowel disease (IBD, Crohn’s disease CD, ulcerative colitis UC). Therefore, our study aimed to investigate the short- and long-term changes of the fecal microbiota composition influenced by the bowel preparation with sodium-picosulphate and magnesium-oxide. Methods IBD patients (inactive or mild) preparing for colonoscopy with bowel preparation were enrolled in the study. Control group (HC) consisted of non-IBD patients who were recommended to undergo colonoscopy due to abdominal complaints. Clinical data, blood and stool samples were collected before colonoscopy (point A), 3 days later (point B) and 4 weeks later (point C) to assess disease activity and the changes of the gut microbiome. Fecal microbiota structure was determined by sequencing V4 region of the 16S rRNA gene. Microbiome structure was determined at family level. Statistical analysis included differential abundance analysis and Mann-Whitney test, values of p<0.05 were considered significant. Results 41 patients (9 CD, 13 UC, 19 HC) were enrolled in our study. After the bowel preparation, alpha diversity in the CD group was lower compared to UC(p=0.01) and control(p=0.02) patients at point B. Alpha diversity of UC patients was significantly higher than CD (p‹0.01) and control (p=0.03) groups at point C. Alpha diversity of UC patients increased from point A to C (p=0.04). However, a decreasing tendency in alpha diversity was observed in patients with CD at A to C period (p=0.26). These changes couldn’t be observed in the control group. Beta diversity showed slight differences between the IBD groups and the control group. After bowel preparation, beta diversity of CD patients immediately (from A to B) changed p=0.03), while beta diversity of UC patients seems to continually change from point A to C(p=0.03). Based on the differential abundance analysis, Clostridiales and Pseudomonadaceae families increased, while Bifidobacteriaceae, Carnobacteriaceae, Veillonellaceae and Pasteurellaceae families decreased in CD patients compared to the HC at point B. The most growing families in HC group were Brucellaceae, Moraxellaceae and Alcaligenaceae at A to B period. Conclusion Our findings may suggest that bowel preparation can result in a significant change in faecal microbial composition in IBD. Microbial alterations recovering earlier in UC patients due to changed mucosa. Reduced alpha diversity and altered abundance in CD may have potential role in disease exacerbation. Further examinations are needed to clarify our pilot results.