(513) Determining the Utility of MRSA Nasal Swabs in a Neuroscience ICU at a Large Academic Medical Center

Introduction: Methicillin-resistant Staphylococcus aureus (MRSA) nasal polymerase chain reaction (PCR) assays have been proven to have high negative predictive value and are commonly used as a tool for de-escalation of empiric anti-MRSA therapy. MRSA nasal swabs have been studied in numerous patient populations, however, the test has yet to be validated in a neurocritically ill population. The objective of this study is to determine the utility of MRSA nasal swabs to identify or rule out MRSA infections in a neuroscience ICU patient population.

Methods: A single-center, retrospective, observational, cohort study of neurocritically ill adult patients was conducted. Patients were excluded if they were pregnant or incarcerated. During the study period, MRSA swabs were sent for any patients being initiated on an anti-MRSA antibiotic with a suspected respiratory source. The primary outcome was the negative predictive value (NPV) of MRSA nasal swabs for MRSA-positive respiratory cultures within 14 days of swab collection. Secondary outcomes included NPV of MRSA nasal swabs for MRSA positive respiratory culture within 3 days of swab collection, positive predictive value (PPV), and overall prevalence of MRSA.

Results: A total of 211 patients were included in the study and accounted for a total of 259 MRSA nasal swabs. The average time from admission to the first MRSA nasal swab was 6 days. The NPV of MRSA nasal swabs within 14 days of positive respiratory culture was 98% and the NPV at 3 days was 99%. The PPV was 52% at 14 days and 47% at 3 days. The overall MRSA colonization prevalence was 8%. Patients who had negative MRSA nasal swabs with negative MRSA respiratory cultures received an average of 3.8 days of vancomycin therapy vs. 4.2 days in patients with positive MRSA respiratory cultures.

Conclusions: This study supports the use of MRSA nasal swabs as a tool for de-escalation of empiric anti-MRSA antibiotic therapy for neuroscience ICU patients with pneumonia.