Methicillin-Resistant Staphylococcus aureus in Early Ventilator-Associated Pneumonia: Cause for Concern?

Background: Ventilator-associated pneumonia (VAP) accounts for almost 90% of infections in mechanically ventilated patients and more than one-quarter of all patients requiring intubation, with associated mortality rates as high as 70%. The rise in methicillin resistance within the community has led to a national increase in methicillin-resistant Staphylococcus aureus (MRSA) rates in early VAP and associated healthcare expenditure. Methods: Trauma patients identified via an institutional VAP database were stratified by gender, age, severity of shock (24-h transfusions), and severity of injury. The primary outcome measure was evaluation of the incidence and trend of early MRSA VAP over a 6-y period. Secondary outcomes examined the adequacy of our current empiric antibiotic regimen as it pertained to outcome variables, including mortality. Results: A total of 997 episodes of VAP were identified in 727 patients. Linear regression showed that the incidence of early Staphylococcus aureus (SA) VAP was stable over the 6-y period (slope=-0.911; p=0.490). Over the same 6y, however, the percentage of MRSA in early SA VAP (slope=3.95; p=0.0154) and the incidence of early MRSA VAP increased. No difference in mortality was detected between early methicillin-susceptible SA and early MRSA VAP. After adjustment for age, ISS, and 24-h transfusion requirements, early MRSA was not an independent predictor of mortality (odds ratio [OR], 0.815; p=0.59). Conclusions: Although the incidence of early SA VAP with methicillin resistance increased significantly within the first 7d of admission, this study showed no difference in mortality and resource utilization between early VAP from MRSA and other causative organisms, despite lack of empiric MRSA coverage.