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 dose cefuroxime/metronidazole versus metronidazole alone in elective colorectal surgery.
Sixty assessable patients undergoing elective colonic and rectal surgery were randomly allocated to receive prophylaxis with a combination of 1.5 g cefuroxime plus 500 mg metronidazole or 500 mg metronidazole alone as single doses by the intravenous route, given at the beginning of anesthesia. The two groups were matched for age, sex, malignancy, and type of operation. Primary wound infections were observed in one patient (3.7%) in the combination group and six (18.2%) in the group given metronidazole alone. This trend was not statistically significant. Bacteriologic examination of the anastomoses, abdominal walls, and wounds showed significantly more sterile cultures in the combination group, although more aerobic cefuroxime-resistant isolates were seen in this group. There is no evidence that the emergence of resistant strains had any influence on the outcome of patients in the study. It was concluded that an appropriate antibiotic prophylactic regimen for colorectal surgery should be directed against aerobic and anaerobic organisms. Cefuroxime plus metronidazole is an effective regimen for the prevention of postoperative infection.