The administration of antibiotic prophylaxis in elective colorectal surgery has reduced surgical site infection (SSI) rate and severity, and decreased post-operative length of stay (LOS). The gold-standard antibiotic prophylaxis is penicillin-based (PBAP). The SSI rate for patients receiving PBAP may differ from those receiving alternative antibiotic prophylaxis regimens (AAP) in cases of reported penicillin allergy. The purpose of this study is to determine if there is a difference in the incidence of 30 day post-operative SSI among elective colorectal surgery patients receiving PBAP as compared with those who receive AAP.

Retrospective chart review of 967 adult elective colorectal procedures completed at Hamilton Health Sciences Corporation between 2009-2015. Eligible patients underwent elective clean contaminated procedures and received antibiotic prophylaxis. Emergent or urgent cases, and dirty wounds were excluded. REDCap Software was used for data collection. Categorical variables were reported as counts and percentages and compared with chi-squares or Fisher’s exact test. Continuous variables were reported as mean and standard deviation, or median with minimum and maximum, and compared with T-tests for independent samples or Mann-Whitney U-test. Univariable analyses were performed to identify candidate variables to include in the multivariable logistic regression (MLR) model. Candidate variables with p≤0.10 were included in the MLR. Odds ratios and 95% confidence intervals and p-vaues were reported. A p-value of 0.05 was set for statistical significance.

Of the 967 elective colorectal procedures reviewed, 86.6% (837) received PBAP and 13.4% (130) received AAP. 157 (16.2%) patients acquired SSI. Four factors contributed to increased SSI risk. If patients received PBAP they were less likely to acquire SSI than if they received AAP (OR 0.63, CI 0.40-0.99). Other contributory factors included BMI over 30 (OR 1.72, CI 1.20 – 2.50), ASA class 3 or 4 (OR 2.35, CI1.05 – 5.26) and planned open surgery (OR 3.35, CI 1.78 – 6.30). If patients acquired an SSI they were more likely to require prolonged LOS (p<0.001) , unplanned hospital visits (38.9%), re-admission (30.6%) and CCAC care (47.8%) for management of SSI.

We conclude that PBAP and AAP regimens may not confer equivalent efficacy in preventing SSI in patients undergoing elective colorectal surgery. AAP in elective colorectal surgery patients is associated with a greater risk of SSI than PBAP. SSI may be associated with longer post-operative LOS, as well as more MD visits, CCAC resource use, and re-admissions. Given these findings, more accurate penicillin allergy testing and reporting is necessary. In order to decrease SSI rates in elective colorectal surgery patients, all eligible patients should receive PBAP, and only truly penicillin-allergic patient should receive AAP.

Surgical site infection rates are higher among colorectal surgery patients receiving non-penicillin based antibiotic prophylaxis:  A retrospective chart review