172. Validation of GeneXpert MRSA/SA Blood Culture Assay in Anaerobic and Pediatric Bottles.
Session: Poster Abstract Session: Diagnostics: Bacteremia
Thursday, October 27, 2016
Room: Poster Hall
  • ID Week 2016 E-poster.JPG (2.2 MB)
  • Background:

    The Cepheid® Xpert® MRSA/SA Blood Culture Assay (GxM) is a qualitative test for the detection of Staphylococcus aureus (SA) or methicillin-resistant Staphylococcus aureus (MRSA) DNA directly from positive blood cultures. The FDA-approval only includes aerobic blood culture bottles. The purpose of this study was to determine whether the GxM performed accurately with both BD-Pediatric and Anaerobic Lytic blood culture bottles.


    1. Discarded anaerobic and pediatric bottles from clinical specimens obtained in the course of care were collected over a 4 week period. These blood culture bottles were tested with GxM and compared to results from MALDI-TOF and BD-Phoenix.

    2. MRSA, MSSA and various quality control strains were spiked into blood culture bottles containing discarded human blood.

    3. Turn-around time comparisons were made between the routine aerobic GxM results and the current methods for pediatric and anaerobic bottles.


    To date, twenty six positive anaerobic blood bottles from 22 patients were obtained: 7 were positive for MRSA, 4 with MSSA, 9 with coagulase negative staphylococci. An additional 6 bottles had: enterococci (2) and 1 each with corynebacterium, E.coli, S.mutans, Morgenella sp.

    Seven pediatric bottles from six patients were obtained. 1 was positive for MRSA, 4 with coagulase negative staphylococci, 1 with Streptococcus thermophiles and Propionibacterium acnes.

    Seventeen anaerobic and pediatric spiked bottles were tested: 10 MRSAs and 1 each of the following: MSSA, and 1 S.hominis, S.agalactiae, M.catarrhalis, S.pyogenes, E.gallinarium and E.facaelis.

    All blood culture bottles from patients or spiked with organisms were either correctly identified or categorized (negative for S.aureus and MRSA) by GxM. The median time from gram stain of an aerobic blood culture to GxM result was 6.5 hours (n=10 random bottles) vs. 27 hours (n = 10) to susceptibility for pediatric and anaerobic bottles via conventional testing.


    These data show that GxM is accurate with anaerobic and pediatric blood culture bottles and expanded use of GxM would provide clinically important information. Study assessing the clinical and cost impact of this technology at our center is ongoing.

    Priyanka Patil, MD1, Wendy Szymczak, PhD1, Iona Munjal, MD2, Philip Gialanella, M.S.1 and Michael Levi, ScD, (D) ABMM3, (1)Pathology, Montefiore Medical Center, Bronx, NY, (2)Pediatric Infectious Disease, The Children's Hospital at Montefiore, Bronx, NY, (3)Pathology, Montefiore Medical Center and the Albert Einstein College of Medicine, Bronx, NY


    P. Patil, None

    W. Szymczak, None

    I. Munjal, None

    P. Gialanella, None

    M. Levi, None

    << Previous Abstract | Next Abstract

    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.