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Evaluation of Discrepancies in Carbapenem Minimum Inhibitory Concentrations Obtained at Clinical Laboratories Compared to a Public Health Laboratory

Published online by Cambridge University Press:  02 November 2020

Julian E. Grass
Affiliation:
Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention, Atlanta, GA
Shelley S. Magill
Affiliation:
Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention, Atlanta, GA
Isaac See
Affiliation:
Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention, Atlanta, GA
Uzma Ansari
Affiliation:
Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention, Atlanta, GA
Lucy E. Wilson
Affiliation:
Maryland Department of Health, Baltimore, MD
Elisabeth Vaeth
Affiliation:
Maryland Department of Health, Baltimore, MD
Paula Snippes Vagnone
Affiliation:
3Minnesota Department of Health, St. Paul, MN
Brittany Pattee
Affiliation:
Minnesota Department of Health, St. Paul, MN
Jesse T. Jacob
Affiliation:
Emory University School of Medicine, Atlanta, GA
Georgia Emerging Infections Program
Affiliation:
Atlanta, GA
Chris Bower
Affiliation:
Georgia Emerging Infections Program, Atlanta, GA
Atlanta Veterans Affairs Medical Center
Affiliation:
Decatur, GA
Foundation for Atlanta Veterans Education and Research
Affiliation:
Decatur, GA
Sarah W. Satola
Affiliation:
Emory University School of Medicine, Atlanta, GA
Sarah J. Janelle
Affiliation:
Colorado Department of Public Health and Environment, Denver, CO
Kyle Schutz
Affiliation:
Colorado Department of Public Health and Environment, Denver, CO
Rebecca Tsay
Affiliation:
New York Rochester Emerging Infections Program at the University of Rochester Medical Center, Rochester, NY
Marion A. Kainer
Affiliation:
Tennessee Department of Health, Nashville, TN
Daniel Muleta
Affiliation:
Tennessee Department of Health, Nashville, TN
P. Maureen Cassidy
Affiliation:
Oregon Health Authority, Portland, OR
Vivian H. Leung
Affiliation:
Connecticut Department of Public Health, Hartford, CT
Meghan Maloney
Affiliation:
Connecticut Department of Public Health, Hartford, CT
Erin C. Phipps
Affiliation:
University of New Mexico, Albuquerque, NM
New Mexico Emerging Infections Program
Affiliation:
Santa Fe, NM
Kristina G. Flores
Affiliation:
University of New Mexico, Albuquerque, NM
New Mexico Emerging Infections Program
Affiliation:
Santa Fe, NM
Erin Epson
Affiliation:
California Department of Public Health, Richmond, CA
Joelle Nadle
Affiliation:
California Emerging Infections Program, Oakland, CA
Maria Karlsson
Affiliation:
Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention, Atlanta, GA
Joseph D. Lutgring
Affiliation:
Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention, Atlanta, GA
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Abstract

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Background: Automated testing instruments (ATIs) are commonly used by clinical microbiology laboratories to perform antimicrobial susceptibility testing (AST), whereas public health laboratories may use established reference methods such as broth microdilution (BMD). We investigated discrepancies in carbapenem minimum inhibitory concentrations (MICs) among Enterobacteriaceae tested by clinical laboratory ATIs and by reference BMD at the CDC. Methods: During 2016–2018, we conducted laboratory- and population-based surveillance for carbapenem-resistant Enterobacteriaceae (CRE) through the CDC Emerging Infections Program (EIP) sites (10 sites by 2018). We defined an incident case as the first isolation of Enterobacter spp (E. cloacae complex or E. aerogenes), Escherichia coli, Klebsiella pneumoniae, K. oxytoca, or K. variicola resistant to doripenem, ertapenem, imipenem, or meropenem from normally sterile sites or urine identified from a resident of the EIP catchment area in a 30-day period. Cases had isolates that were determined to be carbapenem-resistant by clinical laboratory ATI MICs (MicroScan, BD Phoenix, or VITEK 2) or by other methods, using current Clinical and Laboratory Standards Institute (CLSI) criteria. A convenience sample of these isolates was tested by reference BMD at the CDC according to CLSI guidelines. Results: Overall, 1,787 isolates from 112 clinical laboratories were tested by BMD at the CDC. Of these, clinical laboratory ATI MIC results were available for 1,638 (91.7%); 855 (52.2%) from 71 clinical laboratories did not confirm as CRE at the CDC. Nonconfirming isolates were tested on either a MicroScan (235 of 462; 50.9%), BD Phoenix (249 of 411; 60.6%), or VITEK 2 (371 of 765; 48.5%). Lack of confirmation was most common among E. coli (62.2% of E. coli isolates tested) and Enterobacter spp (61.4% of Enterobacter isolates tested) (Fig. 1A), and among isolates testing resistant to ertapenem by the clinical laboratory ATI (52.1%, Fig. 1B). Of the 1,388 isolates resistant to ertapenem in the clinical laboratory, 1,006 (72.5%) were resistant only to ertapenem. Of the 855 nonconfirming isolates, 638 (74.6%) were resistant only to ertapenem based on clinical laboratory ATI MICs. Conclusions: Nonconfirming isolates were widespread across laboratories and ATIs. Lack of confirmation was most common among E. coli and Enterobacter spp. Among nonconfirming isolates, most were resistant only to ertapenem. These findings may suggest that ATIs overcall resistance to ertapenem or that isolate transport and storage conditions affect ertapenem resistance. Further investigation into this lack of confirmation is needed, and CRE case identification in public health surveillance may need to account for this phenomenon.

Funding: None

Disclosures: None

Type
Poster Presentations
Copyright
© 2020 by The Society for Healthcare Epidemiology of America. All rights reserved.