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.
Single or multiple doses of metronidazole and ampicillin in elective colorectal surgery. A randomized trial.
A randomized trial including 294 patients was performed to evaluate the prophylactic effect of single vs. multiple doses of antibiotics in elective colorectal surgery. All patients received 1.5 g metronidazole and 3.0 g ampicillin peroperatively and were randomized to: no further prophylactic antibiotic treatment, or ampicillin 1 g X 3 and metronidazole 0.5 g X 3 given intravenously during the second and third postoperative days. Deep wound infection was seen in 9/149 (6 percent) receiving a single dose and in 8/145 (6 percent) receiving multiple doses. No differences were found in the two groups between frequencies of anastomotic dehiscences, intra-abdominal abscesses, sepsis, and pulmonary infections. The two groups were similar according to distribution of sex, age, diagnosis, and type of surgery. A single peroperative dose of metronidazole and ampicillin is a simple and satisfactory antibiotic prophylaxis in elective colorectal surgery.