Bacteria are critical in determining the outcome of surgical procedure. It is no coincidence that the growth of antisepsis and antibiotics matched with dramatic improvements in mortality and morbidity. For example, in bowel and rectal cancer, colorectal surgery may fail because of anastomotic leak seemingly caused by the metabolization of collagen by the gut microbiota.

According to James Kinross, from the Imperial College London, «perioperative modulation of the gut microbiome is really important to improve not only operative but also oncological outcomes and to ensure that patients have a good quality of life after cancer treatment».