Methicillin-resistant Staphylococcus aureus in early ventilator-associated pneumonia: cause for concern?

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.

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.

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 6 y, 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).

Although the incidence of early SA VAP with methicillin resistance increased significantly within the first 7 d 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.