A national cohort study of just over 79,000 patients undergoing surgery looked to determine if differing durations of surgical prophylaxis resulted in reductions in surgical site infection, and also if there were effects reflected in adverse outcomes such ad acute kidney injury and Clostridium difficile infection. The type of antibiotic regimen was also examined. The procedures included cardiac surgery, orthopaedic total joint replacement, colorectal and vascular procedures performed over a 5 year period. Data were analyzed using multivariable logistic regression, with adjustments for covariates determined a priori to be associated with the outcomes of interest. The duration of postoperative antimicrobial prophylaxis was divided into four categories: <24 hours, 24-<48 hours, 48-<72 hours, and ≥72 hours. The mean (SD) age of the subjects was 64.8 +/- 9.4 years. After stratification by type of surgery and adjustment for age, sex, race, diabetes, smoking, American Society of Anesthesiologists score > 2, methicillin-resistant Staphylococcus aureus colonization, mupirocin, type of prophylaxis, and facility factors, a discernible effect of increased prophylaxis upon surgical site infection could not be demonstrated. Adjusted odds of kidney injury increased with each additional day of prophylaxis, as did the risk of postoperative C difficile infection. Being treated with cancomycin was also a significant risk factor for AKI. The researchers suggest that these findings highlight the need for stewardship efforts to limit duration of prophylaxis, as this approach can reduce adverse events without increasing surgical site infection. Read more here