Impact of preoperative gastrointestinal microbiota on weight loss after Roux-en-Y gastric bypass: a pilot study

Aim: In recent years the composition of gut microbiome has been linked to the development of several diseases. The aim of the following study was to establish whether it is connected with the outcome of bariatric surgery and analyze theoral and gut microbiota of patients suffering from morbid obesity who underwent laparoscopic Roux-en-Y gastric bypass (LRYGB). Material and methods: The following is a prospective cohort study that was conducted between November 2018 and June 2019. Participants underwent LRYGB surgery. Patients were assigned to group 1 - success (surgical participants who achieved a percentage of excess weight loss [%EWL] >50%), or group 2 (surgical participants who achieved a %EWL <50%). The follow-up to establish %EWL was conducted for 6 months after surgery. Before surgery, oral swabs were obtained, and stool samples were provided. The endpoint was the composition of the gut microbiota. Results: Group 1 consisted of 4 participants; group 2 consisted of 2 participants. No participants were lost to follow-up during the study. Participants in group 1 had an oral microbiota that was enriched with Tissirelia bacteria of the phylum Firmicutes. Gut microbiome of patients in group 1 was enriched with Tannerella of the phylum Bacteroidetes. Group 2 did not present microbiota enriched with any of the analyzed organisms. Gut microbiota was enriched with deltaproteobacteria class (phylum Proteobacteria), bernesiellaceae of the phylum Bacteroidetes. Conclusion: The compositions of the microbiota of the oral cavity and large intestine are related to weight loss achieved following LRYGB.