Characteristics and outcomes of methicillin-resistant staphylococcus aureus bloodstream infections in patients with cancer treated with vancomycin: 9-year experience at a comprehensive cancer center

Abstract

Background: Methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infections (BSIs) can cause significant morbidity and mortality in patients with cancer. However, data on outcomes of patients treated with vancomycin are lacking.

Methods: We identified 223 patients with cancer who developed MRSA BSIs between January 2001 and June 2009 and were treated with vancomycin. Treatment failure was defined as death within 60 days of infection, persistent bacteremia ≥5 days, fever ≥4 days, recurrence or relapse, and secondary MRSA infection.

Results: The treatment failure rate was 52% (116 of 223 patients). These patients were more likely to have been hospitalized, been treated with steroids within the previous 3 months, developed acute respiratory distress syndrome, required mechanical ventilation, required intensive care unit care, and community-onset infections (all p < .05). Risk factors for MRSA-associated mortality (27 of 223 patients; 12%) included hematologic malignancy and hematopoietic stem cell transplantation, community-onset infection, secondary BSI, MRSA with minimum inhibitory concentration (MIC) ≥2.0 μg/mL, mechanical ventilation, and a late switch to an alternative therapy (≥4 days after treatment failure; all p < .05). On multivariate analysis, mechanical ventilation and recent hospitalization were identified as independent predictors of vancomycin failure, and community-onset infection, secondary BSIs, and MIC ≥2 μg/mL were identified as significant predictors of MRSA-associated mortality.

Conclusions: We found a high treatment failure rate for vancomycin in patients with cancer and MRSA BSIs, as well as a higher mortality. A vancomycin MIC ≥2 μg/mL was an independent predictor of MRSA-associated mortality. An early switch to an alternative therapy at the earliest sign of failure may improve outcome.

Figure 1.

Distribution of minimum inhibitory concentrations over time for the clinical isolates of methicillin-resistant Staphylococcus aureus bloodstream infections. Abbreviation: MIC, minimum inhibitory concentration.

Figure 2.

Yearwise distribution of methicillin-resistant Staphylococcus aureus bloodstream infections in patients with solid tumors versus hematologic malignancies from 2001 to 2009. *Cases between January 1, 2009 and June 30, 2009. **Includes patients with lymphoma or leukemia, as well as hematopoeitic stem cell transplant recipients.

Figure 3.

Survival curves of patients with methicillin-resistant Staphylococcus aureus bloodstream infections stratified by minimum inhibitory concentrations ≥2 μg/mL versus p = .02). Abbreviation: MIC, minimum inhibitory concentration.