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.
Prophylactic single-dose fosfomycin and metronidazole compared with neomycin, bacitracin, metronidazole and ampicillin in elective colorectal operations.
Two antibiotic regimens for the prophylaxis of infection after colorectal operations were compared in a prospective, double blind, randomised controlled trial in 244 patients. Ninety-five patients (39%) were either excluded before randomisation or withdrawn, leaving 149 for analysis. Group 1 (n = 72) received a single infusion of 8 g fosfomycin and 1 g metronidazole at the induction of anaesthesia. Group 2 (n = 77) received bacitracin 250 mg plus neomycin 250 mg (as four tablets on three occasions over two days), metronidazole 500 mg tablets three times a day for one day, and ampicillin 1 g intravenously at induction of anaesthesia. Nine patients in group 1 (13%), 95% confidence interval (CI) 6.9 to 22.4, developed infective complications, compared with 8 in group 2 (10%), 95% CI 4.6 to 19.4. The overall infection rate was 17 of 149 evaluable patients (11%), 95% CI 6.8 to 17.7. Seven patients died (five in group 1 and 2 in group 2), two of whom (one in each group) died as a direct result of infective complications. Long operations and obesity were the most important risk factors, and may indicate a need for longer prophylaxis. Fosfomycin, which is mainly active against aerobic bacteria, was both safe and useful when combined with metronidazole.