Approximately three-quarters of all invasive MRSA infections in the United States are BSIs. Research shows many patients with MRSA BSIs are not treated with effective definitive therapy even when antibiotic susceptibility results are known. Inappropriate antibiotic selection for MRSA BSI results in poor clinical outcomes.
This study aims to describe the current pattern of antibiotic therapy in patients with MRSA BSI and to evaluate factors that are associated with receiving ineffective definitive therapy.
We performed a retrospective case-cohort study of 562 patients with MRSA BSI from 10 hospitals (1 tertiary and 9 community medical centers) from 1999-2003. Patients were included if they were alive and remained at a study hospital on day 7 following a MRSA BSI. The primary endpoint was the administration of effective definitive therapy for MRSA BSI. Effective definitive therapy was defined as receipt of one or more of the following antimicrobial agents by day 7 after the date of the initial positive blood culture: daptomycin, linezolid, quinupristin/dalfopristin or vancomycin. Multivariable logistic regression was used to determine variables associated with receipt of effective definitive therapy.
A total of 562 patients were studied. Of these 384 were alive and hospitalized at day 7. The mean age of the cohort was 63 years (standard deviation: 16) and 50% were male. 352 (91.7%) patients received appropriate definitive therapy against MRSA. In multivariable analysis, patients were more likely to receive effective therapy if they were white (Odds Ratio (OR) 2.09; 95% Confidence Interval (CI) 1.12-5.73), at a tertiary care center (OR 11.2; CI 2.40-52.67), or on a surgical service (OR 4.07; CI 1.16-14.2). Patients with a central venous catheter (CVC) at the time of admission (OR 0.341; CI 0.14-0.09), a history of connective tissue disease (OR 0.17; CI 0.05-0.59) or peripheral vascular disease were less likely to receive effective definitive therapy (OR 0.338; CI 0.05-0.59).
In our study, 32 (8.3%) patients with MRSA BSI did not receive effective definitive therapy for MRSA. The presence of a central venous catheter at admission, connective tissue disease, and peripheral vascular disease were associated with inappropriate definitive therapy for MRSA BSI. Further studies to clarify these risks and to ensure appropriate definitive therapy for patients with MRSA BSI are needed.