2026 Southeastern Residency Conference

Background: 
Methicillin-resistant Staphylococcus aureus (MRSA) nasal swabs are commonly used to safely discontinue empiric MRSA coverage in patients due to their high negative predictive value (NPV) of greater than 98% for MRSA infections. While MRSA nasal swabs have a high NPV, they are not well studied to guide de-escalation in mechanically ventilated patients. Limited guidance exists on de-escalation in mechanically ventilated patients prior to respiratory culture results leading to continuation of empiric antibiotics for an extended duration. This study aims to evaluate the predictive value and stewardship of MRSA nasal swabs in mechanically ventilated trauma patients with ventilator associated pneumonia (VAP). 

Methods:  
This is a single-center, retrospective prevalence study of adults admitted to the Surgical Critical Care (SCC) service with a traumatic injury who were mechanically ventilated for greater than or equal to 48 hours from January 2020 through January 2025. Patients who received a MRSA nasal swab, bronchoalveolar lavage (BAL), and empiric antibiotics for MRSA pneumonia were included in the study. The primary outcome is to establish positive predictive value (PPV), negative predictive value (NPV), sensitivity, and specificity of MRSA nasal swab results. 

Results: MRSA nasal swabs demonstrated a PPV of 58.3% (95% CI 30.4%-86.2%) while the NPV was 97.1% (95% CI 91.4%-100%), a sensitivity of 87.5% (95% CI 64.6%-100%), and a specificity of 86.8% (95% CI 76.1%-97.6%). The median turnaround time for MRSA nasal swab results was 26.4 hours (IQR 25.5,27.6), compared to 48.7 hours (IQR 44.6,64.3) for BAL culture results. 

Conclusions: This study demonstrates that MRSA nasal swabs possess a high NPV in mechanically ventilated trauma patients with VAP and the rapid turnaround time for MRSA nasal swab results compared to BAL cultures provides a clinical advantage for timely antibiotic de-escalation.