Antibiotics covering aerobic and aerobic bacteria should be delivered orally and intravenously prior to colorectal surgery.  Antibiotics delivered within this framework will reduce the risk of postoperative SWI by at least 75%.  Further research is required to establish the optimal timing and duration of dosing, and frequency of longer-term adverse effects such as Clostridium difficile pseudomembranous colitis.
[Perioperative antibiotic prophylaxis in colon surgery. Metronidazole and tobramycin versus metronidazole alone. A prospective randomized study].
97 patients scheduled to undergo elective surgery for colorectal carcinoma were randomized to receive either three doses of intravenous metronidazole-e and tobramycin or three doses of intravenous metronidazole alone. The first dose was given after induction of general anesthesia, the second at 9 p.m. and the third at 6 a.m. the following day. The study was double-blind, with patients in the metronidazol-alone group given a placebo infusion instead of tobramycin. The overall postoperative infection rate was 19.6% with no statistically significant difference between the two groups. It is concluded that the addition of an aminoglycoside does not afford better protection than prophylaxis with metronidazole alone.