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Patterns of early and late ventilator-associated pneumonia due to methicillin-resistant Staphylococcus aureus in a trauma population.

BACKGROUND
Community-acquired methicillin-resistant Staphylococcal aureus (CA-MRSA) infection is approaching endemic proportions nationally, and it is a potential cause for early ventilator-associated pneumonia (VAP) in the acutely injured patient. We sought to determine the prevalence of early (≤4 days) and late (>4 days) MRSA pneumonia in ventilated multisystem trauma patients and to correlate findings with admission nasal swabs.


METHODS
We performed a review of our prospective trauma and infectious disease data bases for all patients admitted to our surgical intensive care unit with early (≤4 days) and late (>4 days) VAP during a 4-year period. The diagnosis of pneumonia was established by clinical pulmonary infection score >6, bronchoalveolar lavage, and quantitative cultures showing >10 organisms. Nasal swabs for early identification of MRSA carriers were performed routinely at admission.


RESULTS
One hundred seventy-six patients were identified with S. aureus VAP. Patients with MRSA were compared with those with methicillin-susceptible S. aureus (MSSA). There were 47 (27%) early MSSA VAP and only 4 (2.2%) with early MRSA VAP. One hundred twenty-five patients were diagnosed with late VAP. Forty patients (23%) had MRSA VAP and 85 patients (64%) had MSSA VAP. None of the four patients with an early MRSA VAP had positive nasal swabs at admission.


CONCLUSION
Despite an increase of MRSA nationally, we found a low incidence of early and late MRSA VAP in trauma patients, which was not identified by nasal swab screening. On the basis of our results, we question the efficacy of empiric vancomycin therapy in early (≤4 days) S. aureus VAP. Furthermore, nasal swabs were not helpful in identifying patients at risk for MRSA VAP.