The risk factors and prognosis of methicillin-resistant staphylococcus aureus bacteremia: focus on nosocomial acquisition

Kim, Su Hyun; Ryu, Jung Hwa; Kim, Myung Shin; Choi, Hee Jung

Abstract

BACKGROUND: Staphylococcus aureus is the most common pathogen causing nosocomial infection; it contributes significantly to patient morbidity and mortality. The incidence of S. aureus bacteremia in hospitals as well as communities has significantly increased during the past decade. The purpose of this study was to determine the risk factors and prognosis of methicillin-resistant S. aureus bacteremia.
METHODS
We reviewed the medical records of 164 cases of S. aureus bacteremia during 1999-2003 at the Ewha Womans University MokDong hospital. We retrospectively analyzed the cases, which satisfied the definition of clinically significant bacteremia and whose medical records were available.
RESULTS
The number of methicillin-sensitive Staphylococcus aureus infections (MSSA) was 87 cases and methicillin-resistant Staphylococcus aureus (MRSA) 77 cases. There were 65 cases (84.4%) of nosocomial infection, 9 cases (11.7%) of health-care associated and 3 cases (3.9%) of community-acquired MRSA bacteremia. The risk factors associated with nosocomial MRSA were previous use of antibiotics (OR 15.6, p<0.001) and advanced age (OR 4.9, p=0.017). The risk factor for increased mortality in patients with nosocomial S. aureus bacteremia was septic shock (Hazard ratio 13.2, p<0.001).
CONCLUSIONS
MRSA bacteremia was more frequent in patients with previous antibiotic therapy and advanced age. In addition, the risk factor for mortality in patients with S. aureus bacteremia was septic shock. Additional prospective randomized trials to assess the efficacy and initiation of empirical antibiotics in a well matched cohort study are necessary.