Negative Nasal Methicillin-Resistant <i>Staphylococcus aureus</i> (MRSA) Polymerase Chain Reaction Rules Out Future MRSA Infections in Severely Injured Trauma Patients

<b><i>Introduction:</i></b> Studies have shown that methicillin-resistant <i>Staphylococcus aureus</i> (MRSA) polymerase chain reaction (PCR) swabs aid in de-escalating and decreasing the duration of antibiotic use in respiratory infections. However, the utility of MRSA PCR swabs is unknown for severely injured trauma patients. The aim of this study is to determine if negative MRSA PCR nasal swabs are associated with future MRSA infections in trauma patients admitted to the intensive care unit (ICU). <b><i>Methods:</i></b> Trauma patients admitted to the ICU that had a nasal MRSA PCR from July 2022 to March 2024 were evaluated. Demographics, as well as complication rates (including myocardial infarction, stroke, venous thromboembolism, acute respiratory distress syndrome, acute kidney injury), number and site of cultures obtained, days from MRSA PCR to culture, and positivity of a MRSA infection in those cultures, were evaluated. <b><i>Results:</i></b> In the study period, 65 severely injured patients were identified with an infection and nasal MRSA PCR. Most patients were male (74%), suffered a blunt mechanism (85%), and had a 28-day mortality rate of 36.9%. The median injury severity score was 26. Of the 65 injured patients, 7 (10.8%) had a positive MRSA PCR. There were 142 cultures obtained. No patient that had a negative PCR had a positive MRSA infection. The performance characteristics of a MRSA PCR swab included sensitivity (100%), specificity (92%), positive predictive value (29%), and negative predictive value (NPV, 100%). <b><i>Conclusion:</i></b> The incidence of MRSA-positive infections in trauma patients is low with a negative MRSA PCR swab, NPV of 100%. On the basis of these findings, there should be consideration of withholding empiric MRSA coverage in trauma ICU patients with a negative MRSA PCR. This may aid in reducing unnecessary antibiotic initiation and healthcare costs. Larger studies are needed to validate these findings and help delineate patients for which empiric MRSA coverage can be withheld.