Bacteremic pneumonia due to Staphylococcus aureus: A comparison of diseasecaused by methicillin-resistant and methicillin-susceptible organisms

We performed a prospective study of all patients with bacteremic pneumonia due to Staphylococcus aureus over a period of 6 years during an outbreak of methicillin-resistant S. aureus (MRSA). Patients with bacteremic pneumonia due to MRSA (32 cases) or methicillin-susceptible S. aureus (MSSA; 54 case s) were compared. The patients with MRSA pneumonia were older and were more likely than those with MSSA pneumonia to have predisposing factors for acq uisition of the infection. There were no differences in clinical findings, radiological pattern, or complications in clinical evolution among patients with MRSA and MSSA pneumonia. Mortality was significantly higher among MSS A-infected patients treated with vancomycin than among those treated with c loxacillin (47% vs. none; P < .01). Multivariate analysis (stepwise logisti c regression method) showed a relationship between mortality and the follow ing variables: septic shock (odds ratio [OR], 61), vancomycin treatment (OR , 14), and respiratory distress (OR, 8).