Gut firmicutes changes after laparoscopic one anastomosis gastric bypass surgery

Background and aims: bariatric surgery may cause anatomical changes in the digestive system and alter the distribution of gut microbes. we aim to evaluate the changes of firmicutes after the laparoscopic one anastomosis gastric bypass/mini gastric bypass (oagb/ mgb) surgery. methods: fifty patients with morbid obesity were operated on with oagb/ mgb. demographic data and firmicutes counts in stool samples were obtained before, 6, and 12 months after the surgery. the logarithm of firmicutes colony count based on 10 was used for analysis. paired t-test, ancova model, and pearson correlation tests were used for statistical analysis. results: 70.6% of our patients were female. the percentage of excess weight loss (%ewl) and excess bmi loss (%ebmil) were 44.06%±9.84 and 42.56%±5.29 respectively at the 6-month follow-up and 67.55%±5.56 and 70.81%±7.25 respectively at the 12- month follow-up. the firmicutes count was dropped from 1.57 to 1.44 at 6-month (p=0.01) and 1.32 at 12-month (p=0.02) follow-up. ancova model after adjustment for age, sex, preoperative bmi, and delta-bmi did not show a significant difference for either the 6- or 12-months data (p=0.74 and 0.59, respectively). pearson correlation test found no relationship between firmicutes count change any weight-related variables. conclusion: the firmicutes count was significantly decreased after oagb/mgb. however, no significant relationship was found between weight loss and firmicutes count.