Preoperative oral antibiotic prophylaxis reduces surgical site infections after elective colorectal surgery: results from a before-after study

Background. Surgical site infections (SSIs) are common complications after colorectal procedures and remain an important source of morbidity and costs. Preoperative oral antibiotic prophylaxis is a potential infection control strategy, but its effectiveness without simultaneous use of mechanical bowel preparation (MBP) is unclear. In this study, we aimed to determine whether preoperative oral antibiotics reduce the risk of deep SSIs in elective colorectal surgery. Methods. We performed a before-after analysis in a teaching hospital in the Netherlands. Patients who underwent surgery between January 2012 and December 2015 were included. On 1 January 2013, oral antibiotic prophylaxis with tobramycin and colistin was implemented as standard of care prior to colorectal surgery. The year before implementation was used as the control period. The primary outcome was a composite of deep SSI and/or mortality within 30 days after surgery. Results. Of the 1410 patients, 352 underwent colorectal surgery in the control period and 1058 in the period after implementation of the antibiotic prophylaxis. We observed a decrease in incidence of the primary endpoint of 6.2% after prophylaxis implementation. When adjusted for confounders, the risk ratio for development of the primary outcome was 0.58 (95% confidence interval, 0.40-0.79). Other findings included a decreased risk of anastomotic leakage and a reduction in the length of postoperative stay. Conclusions. Preoperative oral antibiotic prophylaxis prior to colorectal surgery is associated with a significant decrease in SSI and/or mortality in a setting without MBP. Preoperative oral antibiotics can therefore be considered without MBP for patients who undergo colorectal surgery.