The Influence of Antibiotic and Mechanical Bowel Preparation on the Microbiome in Colorectal Cancer Surgery: A Pilot Study

The extent to which bowel preparation mechanical (MBP) or oral antibiotic (OA) or in combination (MBP/OA)) should be performed prior to elective colorectal surgery is the subject of ongoing debate. The aim of our study was to investigate the effect of MPB/OA [with single-shot intravenous antibiotic administration before incision (MPB/OA+ivAB)] on the microbiome of patients with colorectal carcinoma (CRC) operated minimally-invasive. We were studying 16 consecutive patients who underwent elective resection surgery for CRC at our centre in a prospective panel study. MBP was performed and 1 g parmomomycin/500 mg metronidazole was administered orally one day preoperatively; 1 g ertapenem was administered intravenously 30 min prior incision. Three mucosal samples were taken preoperatively during colonoscopy and intraoperatively and analysed by 16S rRNA V1-V2 gene sequencing. Before MPB/OA+ivOA, the genera Phocaeicola (10 %), Bacteroides (7 %) and unclassified Ruminococcaceae (6 %) were predominant. After preparation, all bacteria were reduced except Enterococcus (7 %) and Escherichia/Shigella (6 %), which had increased. Significant reductions were seen for Bacteroides (p = 0.01), Haemophilus (p = 0.047), Holdemanella (p = 0.004), Neisseria (p = 0.004), Odoribacter (p = 0.027), unclassified Clostridiales (p = 0.008) and unclassified Ruminococcacaeae (p = 0.009). Large effect sizes (Cohens'd) were seen for Bacteroidetes (d = 0.864) and unclassified Ruminococcacaeae (d = 0.909). In our pilot study, we observed a significant reduction in seven bacterial genera after MBP/OA+ivAB in patients with CRC. Some of these bacterial genera have been associated with anastomotic insufficiency. Further, large in-depth analyses are needed to evaluate perioperative microbial drift with postoperative complications.