Background

Gut microbiome diversity may change following bariatric surgery. We report preliminary findings of a pilot study designed to identify diagnostic or prognostic indicators.

Methods

Patients undergoing SG or RYGB donated stool samples pre- and post-surgery, and intra-operative samples from the small intestinal mucosa (RYGB), gastric mucosa (RYGB and SG), and gastric fluid (SG). Within-patient analyses were possible in 9 patients with both pre- and post-surgery stool samples (n=4, RYGB; n=5, SG) or combinations of mucosal, fluid and > 1 stool sample (n=4). Microbiota was quantified by sequencing the V1-V3 region of the 16 S rRNA gene. Significant differences in microbiota composition with surgery were determined from alpha- and beta-diversity community analysis and abundance of individual taxa.

Results

The abundance of Oscillobacter (p=0.03), Bacteroides fragilis (p=0.043), and Bacteroides nordii (p=0.044) in stool significantly decreased from pre- to post-surgery, while Lactobacillus gasseri increased (p=0.009). The abundances of Lactillobacillus gasseri decreased slightly in all four SG patients and Bacterioides nordii decreased exclusively in RYGB patients. The structural composition of the top 20 genera in stool changed markedly in six patients (4 SG, 2 RYGB), but little in three patients (1 SG, 2 RYGB), again without clear relation to surgery type. Bacterial community composition varied between tissue (mucosal, fluid) and stool samples.

Conclusions

We detected significant changes in gut microbiome before and after bariatric surgery and noted variability between tissue and stool bacterial communities. Further studying of the contribution of tissue microbiome in patients undergoing bariatric surgery is warranted.