Staphylococcus aureus bacteremia: comparison of two periods and a predictive model of mortality

Abstract

Staphylococcus aureus is an important pathogen causing bacteremia, primarily affecting hospitalized patients. We studied the epidemiology of S. aureus bacteremia, comparing two periods (early and mid 1990s) and developed a predictive model of mortality. A nested case-control was done. All 251 patients over 14 years old with positive blood cultures for S. aureus were selected. MRSA (methicillin resistant S. aureus) was isolated in 63% of the cases. When comparing the two periods MRSA community-acquired bacteremia increased from 4% to 16% (p=0.01). There was no significant difference in the mortality rate between the two periods (39% and 33%, p=0.40). Intravascular catheters provoked 24% of the cases of bacteremia and were associated with the lowest rate of mortality. In a logistic regression analysis, three variables were associated with death: septic shock, source of bacteraemia and resistance to methicillin. The probability of dying among patients with MRSA and those with methicillin sensitive S. aureus bacteraemia ranged from 10% to 90% and from 4% to 76%, respectively, depending on the source of the bacteraemia and the occurrence of septic shock. The MRSA found in Brazil may be a particularly virulent strain.

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

“…A study performed in south-east Brazil reported an increasing incidence of community-acquired bacteraemia due to MRSA. 25 In a recent report of 17 hospitals in Australia, 12% of community-onset episodes were MRSA. 26 In the present study, all patients with community-acquired MRSA bacteraemia had received healthcare assistance.…”

Pediatric mortality due to nosocomial infection: a critical approach

“…They found no significant differences in the mortality rates. Based on logistic regression, septic shock, source of bacteremia and methicillin resistance were found to be positively associated with subsequent mortality [18].…”

Staphylococcus aureus bacteremia: what is the impact of oxacillin resistance on mortality?

“…Although data can be found in the literature indicating an increasing incidence of community-acquired oxacillin-resistant S. aureus infections, it can be seen that most studies do not clearly show the criteria used to define community-acquired infection, which is frequently taken as an infection detected by culture within 48 or 72 hours of admission to hospital [2,5]. Based on the criteria adopted in our study, and in view of the greater accuracy of the data resulting from the prospective nature of the study, we did not detect any cases of community-acquired resistant S. aureus.…”

“…A recent study carried out in the Hospital São Paulo showed that 4.4% of the cases of oxacillinresistant S. aureus bacteremias seen there from 1991-92 were community-acquired, whereas the percentage was 15.9% for 1995-96, indicating an increasing trend in our community [5].…”

“…In comparison with the evolution of oxacillinsusceptible S. aureus bacteremias, a previously cited study [5] observed greater mortality for S. aureusresistant bacteremias, while raising the possibility that this may have been due to the greater virulence of the strain detected as dominant in the hospital where it was isolated.…”