Empirical antimicrobial therapy for bloodstream infection due to methicillin-resistant Staphylococcus aureus: no better than a coin toss.

BACKGROUND

Despite the high prevalence of methicillin-resistant Staphylococcus aureus (MRSA) infection in the hospital, the proportion of patients with MRSA bacteremia who receive appropriate empirical therapy remains suboptimal.

OBJECTIVE

To investigate the proportion of patients with MRSA bloodstream infection (BSI) who received appropriate empirical antibiotic therapy and to identify risk factors associated with receipt of appropriate empirical therapy.

METHODS

We studied a cohort of patients from 10 hospitals. The primary outcome was the proportion of patients who received appropriate empirical antibiotic therapy for MRSA BSI. Appropriate therapy was defined as receipt of daptomycin, linezolid, quinupristin-dalfopristin, or vancomycin within 1 calendar day after the first blood culture result positive for S. aureus (ie, before antimicrobial susceptibilities were known). Multivariable logistic regression was used to determine variables associated with receipt of appropriate empirical therapy.

RESULTS

The study included 562 patients with MRSA BSI. The mean (+/-standard deviation) age of the patients was 64 +/- 16 years, and 288 (51.2%) were male. Only 291 (51.8%) patients received appropriate empirical therapy. Patients were more likely to receive appropriate therapy if they required hemodialysis (odds ratio [OR], 1.36 [95% confidence interval {CI}, 1.00-1.85]), had undergone knee or hip arthroplasty (OR, 3.04 [95% CI, 1.21-7.6]), had a central venous catheter at admission (OR, 1.72 [95% CI, 1.01-2.93]), or had a McCabe score of 1 at admission (OR, 1.83 [95% CI, 1.16-2.83]). Bowel incontinence (OR, 0.41 [95% CI, 0.19-0.92]) and BSIs categorized as primary (OR, 0.41 [95% CI, 0.27-0.63]) were associated with a decreased likelihood of receiving appropriate empirical therapy.

CONCLUSIONS

Only half of patients with MRSA BSI received appropriate empirical therapy. Factors associated with receiving appropriate empirical antibiotics included the presence of a central venous catheter at admission and a history of joint arthroplasty. Surprisingly, prior MRSA infection was not predictive of receipt of appropriate antimicrobial therapy.