Title: Evaluating the Impact of Empiric Anti-MRSA Therapy on Length of Stay in Patients Hospitalized with Community-Acquired Pneumonia
Authors: Jessica Giraldo, Dina Kheir, Timmy Do
Institution: AdventHealth Central Florida Division (AH-CFD)
Background Community-acquired pneumonia (CAP) remains one of the leading causes of hospitalization in the United States, contributing to morbidity, mortality, and healthcare costs. The 2019 American Thoracic Society/Infectious Diseases Society of America (ATS/IDSA) guidelines recommend reserving empiric anti-methicillin-resistant Staphylococcus aureus (MRSA) therapy for patients with validated risk factors. Despite these recommendations, anti-MRSA agents are frequently initiated empirically in patients without validated risk factors. Prior studies evaluating empiric anti-MRSA therapy in CAP have primarily focused on clinical outcomes such as 30-day mortality. These studies also reported increased rates of acute kidney injury (AKI), Clostridioides difficile infection (CDI), and prolonged hospitalization with anti-MRSA therapy. This study evaluated whether empiric anti-MRSA therapy impacts hospital length of stay (LOS) among adults hospitalized with CAP in a large, multi-hospital health system.
Methods This retrospective observational cohort study included adults ≥18 years admitted with a diagnosis of CAP across AdventHealth Central Florida Division (AH-CFD) hospitals between January 1, 2023 and December 31, 2024. Exclusion criteria included documented MRSA risk factors, severe immunocompromise (absolute neutrophil count <500 cells/mm³, CD4 <200 cells/mm³, or recent transplant), or ICU admission at presentation. The primary outcome was hospital LOS and secondary outcomes included 30-day all-cause mortality, 30-day hospital readmission, antibiotic-associated adverse events (e.g. AKI and CDI), and time to clinical stability.
Results A total of 178 patients met inclusion criteria, including 92 patients who received empiric anti-MRSA therapy and 86 who received standard CAP therapy. Median hospital LOS was 3.15 days (IQR 2.16–4.81) in the anti-MRSA group compared with 2.79 days (IQR 1.79–4.20) in the standard-therapy group, with no statistically significant difference (p = 0.091).
Thirty-day all-cause mortality occurred more frequently in patients receiving empiric anti-MRSA therapy compared with standard therapy (4.35% vs 2.33%; RR 1.87, 95% CI 0.35–9.95; p = 0.68). Thirty-day readmission occurred significantly more frequently among patients receiving empiric anti-MRSA therapy (15.22% vs 3.49%; RR 4.36, 95% CI 1.30–14.66; p < 0.001). Antibiotic-associated adverse events were also more common in the anti-MRSA group (5.43% vs 0%; RR 10.29, 95% CI 0.58–183.37; p = 0.06). CDI occurred in more patients of the anti-MRSA group when compared to standard-therapy patients (1.09% vs 0%; RR 2.81, 95% CI 0.12–67.98; p = 1.00). Time to clinical stability was assessable in 40 patients in each treatment group. Median time to clinical stability was 2 days (IQR 2–3; p = 0.67) in both the anti-MRSA and standard therapy groups.
Conclusions Empiric anti-MRSA therapy in adults hospitalized with CAP was not associated with shorter LOS, faster clinical stability, or improved mortality. While 30-day readmission occurred significantly more frequently among patients receiving empiric anti-MRSA therapy, antibiotic-associated adverse events, AKI, and CDI were numerically higher but did not reach statistical significance. These findings support guideline recommendations to reserve anti-MRSA therapy for patients with validated risk factors and highlight opportunities for antimicrobial stewardship interventions to reduce unnecessary antibiotic exposure and improve patient safety.
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