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.
Preoperative cell-mediated immunity and duration of antibiotic prophylaxis in relation to postopertive infectious complications. A controlled trial in biliary, gastroduodenal and colorectal surgery.
In a prospective controlled trial, 750 patients undergoing elective biliary, gastric or colorectal surgery were randomized to receive short-term or long-term antibiotic prophylaxis--cefotaxime for biliary or gastric, and gentamicin/metronidazole for colorectal operations. In all patients, delayed cutaneous hypersensitivity was preoperatively assessed by simultaneous application of seven standardized recall antigens. Positive reaction was defined as mean diameter greater than or equal to 2 mm, anergy as no positive reaction to any antigen, and a 'score' as the sum (in mm) of all the mean diameters of positive reactions. There was no significant difference in septic complication or mortality rates following short-term vs. long-term prophylaxis. Anergy was found in 21 patients (2.8%), while 63 (8.4%) scored 2-4 and 666 (88.8%) greater than or equal to 5. The incidence of postoperative infectious complications was 25% in the patients with score less than 5 and 10% in those scoring greater than or equal to 5, and the corresponding mortality was 14.3 and 2.1% (both p less than 0.001). In the group with preoperative scores less than 5, the duration of antibiotic prophylaxis influenced neither postopertive infectious complications nor mortality.