Preoperative Antibiotics and Mechanical Bowel Preparation Impact the Colonic Mucosa Associated Microbiota But Not Anastomotic Leak Rate After Colorectal Resection

BACKGROUND: Alterations in the gastrointestinal microbiome have been associated with increased anastomotic leak risk. Oral antibiotics and bowel preparations may both reduce anastomotic leaks rates. OBJECTIVE: Within patients undergoing colorectal surgery, we aimed to examine the impact of oral antibiotic use, bowel preparation and other perioperative factors on the mucosa associated microbiota and investigated association with anastomotic leak rates. DESIGN: We opportunistically sampled Australian patients undergoing colorectal resection for any indication with anastomosis, mucosal swabs were taken from the proximal and distal extent of the resected specimen immediately after extraction. SETTINGS: A single site, public tertiary referral hospital of 694 beds with an accredited specialist colorectal unit in Newcastle, Australia. PATIENTS: Of 192 patients; 31 patients were identified as receiving oral antibiotics pre-surgery. Thirty-one patients received mechanical preparation and 58 received enema pre-surgery. MAIN OUTCOME MEASURES: The influence of patient factors on mucosa-associated microbiota composition and associations to rate of anastomotic leaks. RESULTS: The leak rate was 15% (N = 28/192). Preoperative oral antibiotic manipulation and bowel preparation minimally affected the mucosa-associated microbiota, but neither were associated with anastomotic leaks. Erythromycin (N = 14/192) had the greatest impact on the mucosa-associated microbiota. Of the different bowel preparation regimes, excluding patients given antibiotics, only fleet enemas (N = 58/161) had a significant impact on the mucosa-associated microbiota. Bowel preparation was not associated with occurrence of anastomotic leaks. There were only subtle differences observed in the mucosa-associated microbiota between anastomotic leaks and non-anastomotic leaks patients. LIMITATIONS: Antibiotic recipient numbers included were modest. CONCLUSIONS: This is the largest series of routine colorectal anastomoses for which the mucosa-associated microbiota adjacent the anastomoses was examined. We show that antibiotics and bowel preparation in the preoperative period exert only limited effects on the mucosa-associated microbiota and conclude that there are no obvious mucosa-associated microbiota characteristics that are predictive for an anastomotic leak.