Epidemiology, treatment, and outcomes of nosocomial bacteremic Staphylococcus aureus pneumonia

Objective: To describe outcomes associated with nosocomial bacteremic Staphylococcus aureus pneumonia (NBSA-P) and to determine whether delay in adequate antimicrobial treatment is a risk factor for negative clinical and microbiological outcomes. Design: Retrospective cohort analysis. Setting: This study was conducted at Detroit Receiving Hospital and University Health Center, which is a 279-bed, level I trauma center in Detroit, MI. Patients: All episodes of NBSAP identified from January 1, 1999, to April 30, 2004. Results: Of 206 patients identified over a 5-year period with positive blood and respiratory cultures for S aureus, 60 patients met strict clinical, radiographic, and microbiological criteria for NBSAP. The overall mean (+/- SD) characteristics include tire following: age, 55.5 +/- 15.0 years; acute physiology and chronic health evaluation 11 score, 20 (range, 3 to 4 1); ICU at onset, 93.3%; mechanical ventilation, 83.3%; length of stay (LOS) prior to NBSAP, 9 days (range, 2 to 81 days); methicillin-resistant S aureus (MRSA) rate, 70%; and all-cause hospital and infection-related mortality (IRM), 55.5% and 40.0%, respectively. Overall, S aureus pneumonia developed late in the patient's hospital stay in ICU patients previously receiving mechanical ventilation and was associated with high crude mortality and HIM rates. No significant difference existed with respect to mortality or infection-related LOS between patients who had received early appropriate antibiotic therapy, vs those who had received delayed appropriate antibiotic therapy at the onset of pneumonia or in patients with methicillin-sensitive S aureus pneumonia vs those with MRSA pneumonia. Conclusion: HIM from NBSAP is high, and standard therapies evaluated at the time of this study resulted in poor clinical outcomes. Delayed therapy was not found to be a predictor of adverse outcomes; however, this lack of ability to detect a difference may he a product of small sample size. These findings suggest that newer agents with enhanced clinical activity in NBSAP are needed and that these should be evaluated in a real-world setting, where outcomes of the most ill patients can be assessed.