Related Experiment Video
Updated: Feb 6, 2026
Subcutaneous Infection of Methicillin Resistant Staphylococcus Aureus MRSA
Published on: February 9, 2011
Methicillin-resistant Staphylococcus aureus nasal swabs predict need for antibiotic coverage in a trauma population
Bryant McLafferty1, Chelsea N Matzko, Lillian Belfi
1Department of Surgery (B.M., C.N.M., J.Z., S.T., D.T., C.M., P.M., J.D., K.N.H.), Tulane University School of Medicine; LCMC Health (L.B.), University Medical Center New Orleans; and Department of Surgery (A.S.), Louisiana State University Health Sciences, New Orleans, Louisiana.
Background:
Methicillin-resistant Staphylococcus aureus (MRSA) nasal swab screening in a general intensive care unit population has been shown to have a high negative predictive value (NPV) and is used to guide antibiotic stewardship. Trauma populations may be more susceptible to hospital-acquired pneumonia. The purpose of this study is to assess the utility of the MRSA nasal swab in predicting MRSA pneumonia in a trauma population. We hypothesize that the NPV of MRSA nasal swabs in the trauma population will be sufficient to rule out MRSA ventilator-associated pneumonia and therefore withhold MRSA empiric antibiotic treatment.
Methods:
A retrospective review of trauma intensive care unit patients who received an MRSA nasal swab from 2020 to 2023 was performed. Positive and negative MRSA nasal swab groups were compared, and sensitivity, specificity, positive predictive value, and NPV were calculated. Methicillin-resistant S. aureus pneumonia was defined as the presence of ≥10 5 MRSA colonies on respiratory culture.
Results:
A total of 163 patients were screened, and 22 patients (13.5%) had positive MRSA nasal swabs. There were no significant differences in age, body mass index, smoking, or chronic obstructive pulmonary disease between the swab positive and swab negative groups. Sensitivity and specificity were 66.7% and 91.8%, respectively, with a positive predictive value of 45.4% and NPV of 96.4%. Five patients (3.1%) developed MRSA pneumonia, and all but one of these had a positive MRSA nasal swab. Area under the curve for the MRSA nasal test was calculated to be 0.793.
Conclusion:
This is one of the largest studies to date to examine the utility of the MRSA nasal swab in the trauma population. The high NPV (96.5%) for the prediction of MRSA culture growth and ventilator-associated pneumonia suggests that MRSA nasal swabs may be a useful tool for antibiotics stewardship in the trauma population. ( J Trauma Acute Care Surg . 2026;100: 901-905. © 2026 American Association for the Surgery of Trauma.).
Level Of Evidence:
Retrospective Cohort Study, Therapeutic Care/Management; Level IV.
Insights
Methicillin-resistant Staphylococcus aureus (MRSA) nasal swabs have a high negative predictive value (NPV) in trauma patients, suggesting they can help guide antibiotic stewardship by ruling out MRSA pneumonia.
Area of Science:
- Infectious Diseases
- Critical Care Medicine
- Clinical Microbiology
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) nasal swab screening is vital for antibiotic stewardship in general ICUs.
- Trauma patients face increased risk for hospital-acquired pneumonia, necessitating specific diagnostic approaches.
- The predictive value of MRSA nasal swabs for MRSA pneumonia in trauma populations requires further investigation.
Purpose of the Study:
- To evaluate the effectiveness of MRSA nasal swabs in predicting MRSA pneumonia within a trauma intensive care unit (ICU) population.
- To determine if a high NPV of MRSA nasal swabs can reliably exclude MRSA ventilator-associated pneumonia (VAP) in trauma patients.
- To assess the potential for withholding empiric MRSA antibiotic treatment based on negative nasal swab results in this cohort.
Main Methods:
- A retrospective cohort study analyzed data from 163 trauma ICU patients who underwent MRSA nasal swabbing between 2020 and 2023.
- Key performance metrics including sensitivity, specificity, positive predictive value, and negative predictive value (NPV) were calculated.
- MRSA pneumonia was confirmed by respiratory culture yielding ≥105 MRSA colonies.
Main Results:
- Out of 163 patients, 22 (13.5%) had positive MRSA nasal swabs. No significant demographic or comorbidity differences were observed between swab-positive and swab-negative groups.
- The MRSA nasal swab demonstrated a sensitivity of 66.7%, specificity of 91.8%, positive predictive value of 45.4%, and a high NPV of 96.4%.
- Five patients (3.1%) developed MRSA pneumonia, with four of these having positive MRSA nasal swabs. The area under the curve was 0.793.
Conclusions:
- The study highlights the high NPV (96.5%) of MRSA nasal swabs in predicting MRSA pneumonia and culture growth in trauma patients.
- MRSA nasal swabs appear to be a valuable tool for guiding antibiotic stewardship decisions in this specific high-risk population.
- These findings support the potential use of MRSA nasal swabs to safely withhold empiric MRSA antibiotic therapy for VAP in trauma patients.
Related Concept Videos
01:30Development of Antibiotic Resistance
00:57Antibiotic Selection
02:04Conservation of Small Populations
02:27Predicting Molecular Geometry
01:25What is Population Genetics?
00:57Population Growth