Antimicrobial Stewardship Impact on the Treatment of Intra-abdominal Infections in the Surgical Intensive Care Unit

Background: Broad-spectrum antibiotic agents are utilized for complicated intra-abdominal infection (cIAI); however, the need for empiric methicillin-resistant Staphylococcus aureus (MRSA) coverage is not clear as the incidence of MRSA cIAI is rare. Patients and Methods: A single-center, retrospective, pre- and post-cohort study of adults admitted to the surgical intensive care unit (SICU) with cIAI between March 1, 2021, to May 1, 2023, was conducted. Historically, the SICU utilized vancomycin for all cIAI; however, in April 2022, the preferred regimen was changed to either piperacillin-tazobactam with vancomycin added for patients with MRSA risk factors or for Enterococcus spp. coverage in cefepime- or levofloxacin-based regimens for penicillin-allergic patients. The primary outcome was number of vancomycin days of therapy (DOT) per 1,000 patient days. Categoric and continuous variables were analyzed with chi-square and Fisher exact tests. Results: A total of 142 SICU encounters were included, 64 in the pre-cohort and 78 in the post-cohort. There was no difference in median vancomycin DOT per 1,000 patient days (14 days [interquartile range or IQR 5-21]; 16 days [IQR 8-17] p = 0.522) between the pre- and post-cohort. There was a significant reduction in the number of patients given vancomycin after the protocol change (90.6%; 76.9%, p = 0.042). A significant increase in piperacillin-tazobactam exposure was also observed (48.4%; 82.1%, p < 0.001) in the post-cohort aligning with our institutional practice change. Conclusions: In critically ill surgical patients with cIAI, the implementation of an antimicrobial stewardship guideline did not reduce vancomycin DOT per 1,000 patient days, however, it did result in a significant reduction in vancomycin exposure.