Nosocomial, methicillin-resistant Staphylococcus aureus bacteremia: Is it any worse than nosocomial methicillin-sensitive sensitive Staphylococcus aureus bacteremia

OBJECTIVE: To determine the comparative virulence of methicillin-resistant Staphylococcus aureus (MRSA) and methicllin-sensitive S aureus (MSSA) by co nsideration of predisposing factors and outcomes in patients infected with these organisms in the healthcare setting. DESIGN: Analysis of an historical cohort of 504 bacteremic patients (316 MS SA and 188 MRSA), examining factors associated with mortality. SETTING: A 916-bed, university-affiliated, tertiary referral hospital. RESULTS: Risk factors for the development of MRSA include male gender, admi ssion due to trauma, immunosuppression, presence of a central vascular line or an indwelling urinary catheter, and a past history of MRSA infection. O verall mortality was 22%. Death due to bacteremia was significantly greater in the MRSA group (risk ratio, 1.68; P<.05), although these patients were not found to be more likely to die due to underlying disease during treatme nt of bacteremia. In those patients who recovered from bacteremia, no signi ficant differences for the outcome of death could be determined between the MRSA and MSSA groups. CONCLUSIONS: There is a general consensus in the published literature that MRSA bacteremia is more likely to be associated with death, and we confirm this conclusion. However, in contrast to other studies, our MRSA cohort doe s not appear to be more at risk of death due to underlying disease during t reatment for bacteremia. Similarly, the general consensus that MRSA patient s have an increased overall mortality was not confirmed in our study. Diffe rences in comorbidities of patients may provide some explanation of these c onflicting results, while an alternate explanation is that MRSA strains are more virulent than MSSA in some centers. Perhaps the most plausible explan ation is that treatment is provided earlier and in a more aggressive fashio n in some centers, leading to an overall lower mortality rate in all staphy lococcal bacteremias in these institutions (Infect Control Hosp Epidemiol 2 000;21:645-648).