1602. Characterization of Carbapenem-resistant Enterobacteriaceae Isolates Collected through the Emerging Infections Program Network
Session: Poster Abstract Session: Multidrug-Resistant Gram Negative Rods
Saturday, October 5, 2013
Room: The Moscone Center: Poster Hall C
  • Bulens_MuGSI_ID_Week_Poster_FINAL.pdf (1.6 MB)
  • Background: Preventing carbapenemase-producing (CP), carbapenem-resistant Enterobacteriaceae (CRE) transmission is a priority, but determining CP-CRE is complicated because phenotypic testing done in clinical labs does not distinguish CP-CRE from other resistance mechanisms. We assessed a CRE surveillance definition by re-testing isolates identified as CRE in clinical labs using reference susceptibility methods.

    Methods: During 12/2011-2/2013, 4 Emerging Infections Program (EIP) sites submitted Escherichia coli, Enterobacter spp., and Klebsiella  spp. sterile sites or urine isolates that met the EIP CRE definition (carbapenem nonsusceptible (NS) [excluding ertapenem] and resistant to all 3rd generation cephalosporins tested) by minimum inhibitory concentration (MIC) results, as tested on local lab’s automated testing instruments (ATI). CDC performed reference susceptibility testing by broth microdilution, modified Hodge test, and carbapenemase polymerase chain reaction.

    Results: Of 47 isolates, 15 (32%) did not meet the CRE definition after reference testing.  The proportions of E. coli (3/7, 43%) and Enterobacter (11/26, 42%) not meeting the case definition were similar, but was lower for Klebsiella (1/14, 7%).  Isolates not meeting the definition were more likely to have initially tested NS to only 1 carbapenem compared to those that met the definition (13/15 vs. 17/32, p=.03) on the ATI.   ATI MIC results for isolates not meeting the definition were generally ≥ 2 doubling dilutions higher when compared to the reference method MIC.  Isolates that met the definition were significantly more likely to be CP-CRE (20/32 vs. 0/15; p<0.001). Modifying the definition to require resistance, rather than NS, to any carbapenem tested (including ertapenem) eliminated 9/15 isolates  the CRE definition after reference testing, without excluding any CP isolates.

    Conclusion: Many isolates meeting the EIP CRE definition at local labs did not meet the definition following reference testing. This issue was common among Enterobacter spp. and E. coli; ATI MICs were frequently ≥2 doubling dilutions higher, suggesting the difference might not be due to testing variation.  A CRE definition change requiring resistance, to any carbapenem tested might improve the use of this definition for regional or national surveillance.

    Sandra Bulens, MPH1, David Lonsway, MMSc2, Tatiana Travis, BS2, J. Kamile Rasheed, PhD2, Brandi Limbago, PhD2, Ruth Lynfield, MD3, Kristin M Shaw, MPH, CIC4, Paula M Snippes Vagnone, MT (ASCP)4, Jesse Jacob, MD5,6, Jessica Reno, MPH6,7,8, Wendy Bamberg, MD9, Sarah Jackson Janelle, MPH10, Zintars G. Beldavs, MS11, Margaret Cunningham, MPH11 and Alexander Kallen, MD, MPH2, (1)Centers for Disease Control and Prevention, Division of Healthcare Quality Promotion, Atlanta, GA, (2)Division Of Healthcare Quality Promotion, Centers for Disease Control and Prevention, Atlanta, GA, (3)Acute Disease Investigation and Control, Minnesota Department of Health, St. Paul, MN, (4)Minnesota Department of Health, St. Paul, MN, (5)Emory University School of Medicine, Atlanta, GA, (6)Georgia Emerging Infections Program, Decatur, GA, (7)Atlanta Veterans Affairs Medical Center, Decatur, GA, (8)Atlanta Research and Education Foundation, Decatur, GA, (9)Colorado Dept. of Public Health and Environment, Denver, CO, (10)Colorado Department of Public Health and Environment, Denver, CO, (11)Oregon Health Authority, Portland, OR


    S. Bulens, None

    D. Lonsway, None

    T. Travis, None

    J. K. Rasheed, None

    B. Limbago, None

    R. Lynfield, None

    K. M. Shaw, None

    P. M. Snippes Vagnone, None

    J. Jacob, None

    J. Reno, None

    W. Bamberg, None

    S. Jackson Janelle, None

    Z. G. Beldavs, None

    M. Cunningham, None

    A. Kallen, None

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