Addition of metronidazole to standard of care perioperative prophylaxis at time of hysterectomy for gynecologic malignancies

The purpose of this study was to evaluate whether the combination of cefazolin or a second-generation cephalosporin plus metronidazole is associated with a reduced risk of surgical site infection in women undergoing hysterectomy for gynecologic cancer compared to using cefazolin or a second-generation cephalosporin alone. This was a retrospective cohort study of patients who underwent hysterectomy at a single institution between January 2020 and June 2022. The primary outcome was surgical site infection. All patients who underwent abdominal, robotic-assisted, or laparoscopic hysterectomy for presumed malignancy and received either a first- or second-generation cephalosporin with or without metronidazole, or gentamicin with clindamycin, were included in the analysis. A total of 1055 patients were identified who underwent hysterectomy for malignancy during the study period across 4 hospital sites within our system. The overall rate of any surgical site infection was 3.2% (N = 34). Surgical site infection was found to be independently associated with diabetes (p < .01), smoking (p < .01), and antibiotic regimen (p = .04). Surgical site infection rates were 4.3% among patients treated with standard-of-care antibiotics and 2.1% with the addition of metronidazole. However, after adjusting for covariates using a mixed-effects binary logistic regression, the addition of metronidazole to standard-of-care antibiotics was not statistically significantly associated with a reduced risk of surgical site infection (OR 0.5, 95% CI 0.3 to 1.1). While there was evidence supporting an independent association between antibiotic regimen and surgical site infection rate, after adjusting for open incision, smoking status, and diabetes, there was no statistical difference in infection rates with the addition of metronidazole. Future studies with larger sample sizes are warranted to better elucidate these potentially important clinical effects.