Staphylococcus aureus bacteraemia: incidence, risk factors and predictors for death in a Brazilian teaching hospital

The aim of this study was to evaluate the incidence of bloodstream infection due to Staphylococcus aureus and the risk factors for mortality. The design was a two-year retrospective cohort of patients more than one year of age with clinically significant and microbiologically documented bloodstream infection due to S. aureus between January 2000 and December 2001 in a tertiary teaching hospital in midwest Brazil. One hundred and eleven patients were identified with clinically significant and microbiologically confirmed bacteraemia due to S. aureus, accounting for an infection rate of five per 1000 admissions. Nosocomial infections represented 83.8% of cases and meticillin-resistant Staphylococcus aureus (MRSA) accounted for 60.2% of cases. Overall mortality due to S. aureus bacteraemia was 35.1%. Infection due to MRSA, severity of clinical status (severe sepsis or septic shock) and inadequate initial antimicrobial therapy were identified by univariate analysis as predictors of mortality. After Cox regression analysis, severity of clinical manifestations [hazard ratio (HR) 6.86, 95% confidence interval (CI) 3.05-15.43] and inadequacy of antimicrobial therapy (HR 2.27, 95%CI 1.02-5.09) remained as risk factors for mortality. Early diagnosis of bacteraemia should be sought in order to implement adequate treatment before the onset of severe sepsis and septic shock, thus reducing the mortality rate.