Background: Treatment of methicillin-susceptible Staphylococcus aureus (MSSA) bacteremia with antipseudomonal beta-lactams (APBLs) is a common clinical practice in confirmed or suspected polymicrobial infections. Limited data exist to evaluate the impact of APBL treatment on outcomes in MSSA bacteremia. Objectives: To determine whether differences in outcomes exist between patients with MSSA bacteremia treated with cefazolin/oxacillin (standard of care; SOC) versus APBLs. Design: Retrospective cohort study. Methods: Adult and pediatric patients hospitalized between June 2016 and June 2023 with at least one positive blood culture for MSSA who received at least 14 consecutive days of inpatient therapy with cefazolin, oxacillin, cefepime, piperacillin–tazobactam, or meropenem were included. Patients who received APBLs were compared to those who received SOC. The primary outcome was composite clinical failure (i.e., 30-day all-cause mortality and/or bacteremia recurrence within 30 days). Secondary outcomes included 60-day all-cause mortality, intensive care unit and hospital length of stay, 30-day readmission, time to bacteremia clearance, time to mortality, and adverse events (i.e., Clostridioides difficile infection, hepatotoxicity, and acute kidney injury). Results: One hundred patients were included, with 50 patients in each group. The most common source of bacteremia was catheter-related (28% total), and twice as many patients met criteria for complicated MSSA bacteremia in the SOC versus APBL group (80% vs 40%, p < 0.0001). Three patients (6%) in the APBL group met the composite primary outcome compared to 1 (2%) in the SOC group ( p = 0.62). There were no significant differences in secondary outcomes. Conclusion: No differences in mortality or bacteremia recurrence were identified among patients with MSSA bacteremia treated with APBLs compared to SOC. Larger studies should be performed to confirm these findings.
Fielding et al. (2025) studied this question.