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.
Oral is superior to systemic antibiotic prophylaxis in operations upon the colon and rectum.
The prophylactic effect of a short preoperative loading dose of oral neomycin and erythromycin upon infectious complications following elective operations upon the colon and rectum was compared with the prophylactic effect of systemic administration of metronidazole and gentamicin preoperatively and postoperatively. In this randomized prospective clinical study, 45 patients received neomycin-erythromycin while 48 received metronidazole-gentamicin; all patients were prepared mechanically using whole gut irrigation with a mannitol solution. Both groups were comparable in sex, age, clinical diagnosis and type of operation performed. In the neomycin-erythromycin group, 41 of 45 patients had an uncomplicated postoperative course versus 35 of 48 patients in the other group (p less than 0.001) and fewer wound infections (p less than 0.05). We conclude that the better results observed with the neomycin-erythromycin combination is probably an addition of two effects--the decrease in colon flora and the adequate serum levels of antibiotics during the operation.