293. Using MRSA Screening Tests to Predict Methicillin Resistance in Staphylococcus Aureus Bacteremia 
Session: Poster Abstract Session: HAI: MSSA, MRSA, and other Gram-Positives
Thursday, October 27, 2016
Room: Poster Hall
  • IDWeek_MRSA.pdf (437.9 kB)
  • Background: Methicillin resistant Staphylococcus aureus (MRSA) is a clinically significant pathogen for which empiric therapy is often given. However, vancomycin overuse can be associated with significant harm such as nephrotoxicity and increase in healthcare costs. We hypothesized that MRSA screening results could predict methicillin resistance in S. aureus bacteremia prior to final antibiogram result, and curtail inappropriate vancomycin use.

    Methods: We reviewed S. aureus bloodstream infections over a five-year period at two adult tertiary care hospitals at the McGill University Health Center, and determined if MRSA bacteremia could be predicted based on screening swab results. We evaluated MRSA colonization in three ways: known MRSA carrier within 30 days of bacteremia (30-Day Criteria), known MRSA carrier at 30 days or more remotely (All-Time Criteria), and all patients at all time including those untested for MRSA colonization (Inclusive Criteria).

    Results: A negative screening swab within 30 days was done in 235 patients, and yielded negative predictive values of 90% and 95% if the prevalence of MRSA in Staphylococcus aureus bacteremia was less than 39.7% and 23.8% respectively. In such centers, empiric vancomycin could be deferred in most stable patients. Graphs of negative predictive values of screening test and their 95% confidence intervals as a function of MRSA bacteremia prevalence are included below. Results for the inclusive criteria were similar. Conversely, in patients with prior MRSA, the positive predictive value was above 50% even at low prevalence; hence, empiric vancomycin therapy would be appropriate.

    Conclusion: Known MRSA screening test results can help in avoiding unnecessary empiric vancomycin treatment and its complications in settings with low-moderate prevalence of MRSA bacteremia.

    Guillaume Butler-Laporte, MDCM1, Matthew P. Cheng, MD2, Alexandre P. Cheng, BSc3, Emily Mcdonald, MDCM, MSc1,4 and Todd C. Lee, MD, MPH1,2,4, (1)Department of Medicine, McGill University, Montréal, QC, Canada, (2)Department of Microbiology, McGill University, Montréal, QC, Canada, (3)École Polytechnique de Montréal, Montréal, QC, Canada, (4)Clinical Practice Assessment Unit, McGill University, Montréal, QC, Canada


    G. Butler-Laporte, None

    M. P. Cheng, None

    A. P. Cheng, None

    E. Mcdonald, None

    T. C. Lee, None

    Findings in the abstracts are embargoed until 12:01 a.m. CDT, Wednesday Oct. 26th with the exception of research findings presented at the IDWeek press conferences.