1495. Effect of Inoculation Method on Anti-Staphylococcal Antibiotic Utilization and Clinical Outcomes in Methicillin-Resistant Staphylococcus aureus (MRSA) Bacteremia
Session: Poster Abstract Session: Antimicrobial Stewardship: Role of Diagnostics
Saturday, October 10, 2015
Room: Poster Hall
  • Frye_ID Week Poster.pdf (895.5 kB)
  • Background: Increasing concern surrounding the use of vancomycin for MRSA infections with minimum inhibitory concentrations (MICs) > 1 mcg/mL underscores the importance of appropriate lab technique for MIC determination. Our institution utilizes MicroScan Walkaway panels and in July 2013, changed from the Prompt inoculation method to the Turbidity method due to concern for MIC overestimation with the Prompt method. The purpose of this study was to assess the impact of changing bacterial inoculation methods utilized for vancomycin MIC determination on antibiotic selection and the subsequent clinical outcomes in patients with MRSA bacteremia.

    Methods: This study was a retrospective chart review. All adult patients with a blood culture positive for MRSA from July 2012 to June 2013 (Prompt) and July 2013 to June 2014 (Turbidity) were considered for inclusion. Patients were excluded if they had a documented vancomycin or daptomycin allergy, polymicrobial bacteremia, concomitant pneumonia, received vancomycin or daptomycin for < 72 hours, or were transferred from another facility. The primary endpoint was the difference in daptomycin utilization between the Prompt and Turbidity arms. Secondary endpoints included differences between arms in clinical failure, defined as a composite of persistent bacteremia and 30-day in-hospital mortality, percent of patients with an initial vancomycin MIC of 2 mcg/mL, length of stay, hospital readmission, and recurrence of MRSA bacteremia.

    Results: A total of 54 patients met criteria for study inclusion (Prompt = 31, Turbidity = 23). The Turbidity arm had a significant reduction in daptomycin utilization compared to the Prompt arm (11.9 and 30.4 days of daptomycin therapy per 100 days of anti-MRSA therapy, respectively; p = < 0.001) while clinical failure occurred at a similar rate in both the Turbidity and Prompt arms (26.1% and 25.8%, respectively; p = 0.981). There was also a significantly lower percent of patients with an initial vancomycin MIC of 2 mcg/mL in the Turbidity vs. Prompt arm (13% and 38.7%, respectively; p = 0.022).

    Conclusion: For MRSA bacteremia, lower reported MIC values observed using the Turbidity method may lead to decreased daptomycin utilization without impacting clinical outcomes. Larger studies are needed to further validate these results.

    Jessica Frye, PharmD1, Dimple Patel, PharmD, BCPS-AQ ID1, Esther King, PharmD1, John Mcguire, MPA, BS, BT2 and Joel Maslow, MD, PhD, MBA3, (1)Pharmacy, Atlantic Health System, Morristown, NJ, (2)Microbiology, Atlantic Health System, Morristown, NJ, (3)Medicine, Atlantic Health System, Morristown, NJ


    J. Frye, None

    D. Patel, None

    E. King, None

    J. Mcguire, None

    J. Maslow, None

    Findings in the abstracts are embargoed until 12:01 a.m. PDT, Wednesday Oct. 7th with the exception of research findings presented at the IDWeek press conferences.