(P27-002-24) Variability in Gut Microbiota Composition and Dietary Intake Before and After a Health Screening Colonoscopy

Objectives: Repopulation of colonic microbial load after a colonoscopy occurs, however the timing of natural repopulation has not been studied in this setting. Further, no study to date has documented detailed free-living dietary intakes concurrently with gut microbiome repopulation post-colonoscopy. Here we sought to determine the early pattern of repopulation relative to diet.

Methods: Healthy adults (n=15 [4 female/11 male], BMI=27.2±3.9 kg/m², age 51.4±7.2 y) with overweight or obesity who were scheduled to undergo a screening colonoscopy were recruited from the Gastroenterology Clinic at the University of Missouri. Fecal sampling was performed within 2 weeks prior to the colonoscopy (baseline) and on post-colonoscopy days 3, 5, 8, 11, and 14. At baseline, subjects completed detailed food records for 3 days. Post-colonoscopy, subjects ate their free-living diets and detailed food records were collected on days 1, 2, 4, 7, and 10. Gut microbiome composition was assessed by 16S rRNA amplicon sequencing.

Results: Within 5 days after the procedure, subjects reported consuming more total daily energy relative to baseline, presumably to make up for the low energy intake that occurred during the bowel-prep. At baseline, fiber intake (21.3±2.4 g/d) was higher than on post-colonoscopy day 1 (16.4±2.9, p=0.008). Thereafter, daily fiber intake was the same as baseline. Marked intersubject microbiome beta diversity was observed by principal coordinate analysis using weighted and unweighted dissimilarities (p=0.0001, F=15.23, one-way PERMANOVA). Select taxa were depleted acutely post-colonoscopy (e.g., within the Firmicutes phylum). Specifically, significant effects of time were observed between baseline and day 3 fecal samples (pairwise p= 0.0013, F=2.9). These changes normalized by day 5 and with subsequent samples, taxa remained similar to baseline when tested using a weighted dissimilarity analysis (Bray-Curtis).

Conclusions: These results quantitatively demonstrate the magnitude of the significant decline in microbial relative abundance and diversity immediately post colonoscopy. The timing of repopulation aligned with changes in fiber intake post-procedure. These data highlight the importance of nutrition after a screening colonoscopy in reestablishing a healthy microbiome.

Funding Sources: University of Missouri School of Medicine TRIUMPH grant