Impact of oral antibiotic prophylaxis on surgical site infection after rectal surgery: results of randomized trial.

Aim: To evaluate the impact of oral antibiotic prophylaxis on surgical site infection (SSI) rate after rectal surgery.

Methods: It was a single-center 1:1 randomized controlled open parallel trial (registration number NCT03436719). The patients undergoing rectal resection for benign and malignant tumors were assigned randomly to two groups: the oral plus intravenous (IV) antibiotic prophylaxis (AP) and the IV antibiotic prophylaxis only. The primary endpoint was the overall rate of SSI.

Results: Between November 2017 and December 2018, 116 (male-55, the mean age-64 years) patients were enrolled into the trial. Of them, 57 had oral erythromycin 500 mg + metronidazole 500 mg a day before surgery and 1,000 mg of cephalosporin IV 30-90 min before operation. In the other group, 59 patients had the same IV antibiotics only. The incidence of SSIs was 22% (13/59) and 3.5% (2/57) correspondingly (р = 0.002). The statistically significant difference was detected for superficial SSI 0 (0%) vs. 5 (8.5%) (p = 0.03) and organ/space SSI 2 (3.5%) vs. 9 (15.3%) (p = 0.03), respectively. A multivariate analysis of risk factors of SSI identified two independent ones: bacterial contamination of the pelvic cavity ≥ 10 CFU at the end of surgery OR 17.9, 95% CI 2.1-150.0 (p = 0.008) and oral antimicrobial prophylaxis OR 0.2, 95% CI 0.03-0.8 (p = 0.02).

Conclusion: Oral-parenteral AP significantly reduced the risk of SSI following elective rectal surgery. Bacterial contamination of the pelvic cavity ≥ 10 CFU at the end of surgery and oral antimicrobial prophylaxis were independent risk factors of SSI.