227. Effect of MALDI-TOF on the Time to Antibiotic De-escalation in Patients with Positive Blood Cultures: A Retrospective Study Using a Combined ICU Model
Session: Poster Abstract Session: Antimicrobial Stewardship in Clinical Practice
Friday, October 21, 2011
Room: Poster Hall B1
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  • Background: 

    Matrix-assisted laser desorption ionization time of flight (MALDI-TOF) uses mass spectroscopy to create a bacterial species-specific spectral profile based proteins. MALDI-TOF enables identification of bacterial isolates within 30 minutes of initial blood culture positivity, potentially allowing earlier de-escalation of empiric antibiotic therapy. We examined the impact of MALDI-TOF identification on the theoretical time to initial de-escalation of antibiotic spectrum and costs.


    Our clinical laboratory completed a validation of the MALDI-TOF Biotyper (Bruker Daltonics, Billerica MS) and Sepsityper Kit (Bruker) for the identification of bacterial and yeast isolates from positive blood cultures. The MALDI-TOF result was not available for clinical use. A retrospective chart review was performed for patients with positive cultures used in the validation study. Data collected included the time to identification using MALDI-TOF and traditional culture methods as well as start and stop times of all antibiotics. We calculated the reduction in empiric antibiotic duration and cost difference in patients undergoing de-escalation based on traditional blood culture results. Using average wholesale price, the potential cost of starting the de-escalated antibiotic therapy at the time of MALDI-TOF result was compared to actual antibiotic cost.


    110 positive blood cultures were included in the validation study from 1/4/2011 to 4/1/2011. Cultures positive for yeast, polymicrobial cultures, and specimens from patients from other institutions were not included yielding 58 total positive cultures.  MALDI-TOF correctly identified the bacterium present in 53 positive cultures. Forty-one patients were on empiric antibiotics, 27 of which underwent antibiotic de-escalation based on traditional identification.  





    p value

    Empiric Antibiotic Duration (IQR, hrs)

    66.6 (44.4-87.5)

    15.5  (1.4-21.3)

    51.6 (41.8-71.6)


    Median Antibiotic Cost (USD)






    MALDI-TOF allows for rapid bacterial identification leading to a potentially significant reduction in the duration of empiric antibiotic therapy and cost for patients with positive blood cultures.

    Subject Category: J. Clinical practice issues

    Jasmeet Paul, MD1, David Milia, MD1, William Peppard, PharmD, BCPS2, Nathan Ledeboer, PhD, D(ABMM)3, Blake Buchan, PhD3 and Karen Brasel, MD, MPH1, (1)Division of Trauma/Critical Care, Department of Surgery, Medical College of Wisconsin, Milwaukee, WI, (2)Pharmacy Department, Froedtert Memorial Lutheran Hospital, Milwaukee, WI, (3)Department of Pathology, Medical College of Wisconsin, Milwaukee, WI


    J. Paul, None

    D. Milia, None

    W. Peppard, None

    N. Ledeboer, None

    B. Buchan, None

    K. Brasel, None

    Findings in the abstracts are embargoed until 12:01 a.m. EST Thursday, Oct. 20 with the exception of research findings presented at IDSA press conferences.