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.
A comparison of aztreonam/metronidazole and cefotaxime/metronidazole in elective colorectal surgery: antimicrobial prophylaxis must include gram-positive cover.
Aztreonam/metronidazole and cefotaxime/metronidazole were compared in a prospective trial in 154 patients undergoing elective colorectal surgery. Three antibiotic doses were given over 16 hours. A significant excess of wound sepsis in the aztreonam group was seen (23/71 vs 9/70 chi 2 6.60; P less than 0.01). Sepsis was almost invariably due to Gram-positive organisms and, in particular, Staphylococcus aureus.