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Volume 21, Number 9—September 2015
THEME ISSUE
Emerging Infections Program
Emerging Infections Program

Improved Phenotype-Based Definition for Identifying Carbapenemase Producers among Carbapenem-Resistant Enterobacteriaceae

Nora Chea, Sandra N. Bulens, Thiphasone Kongphet-Tran, Ruth Lynfield, Kristin Shaw, Paula Snippes Vagnone, Marion Kainer, Daniel Muleta, Lucy Wilson, Elisabeth Vaeth, Ghinwa Dumyati, Cathleen Concannon, Erin C. Phipps, Karissa Culbreath, Sarah J. Janelle, Wendy Bamberg, Alice Y. Guh, Brandi M. Limbago, and Alexander J. KallenComments to Author 
Author affiliations: Centers for Disease Control and Prevention, Atlanta, Georgia, USA (N. Chea, S.N. Bulens, T. Kongphet-Tran, A.Y. Guh, B. Limbago, A.J. Kallen); Minnesota Department of Health, St. Paul, Minnesota, USA (R. Lynfield, K.M. Shaw, P. Snippes Vagnone); Tennessee Department of Health, Nashville, Tennessee, USA (M.A Kainer, D.B. Muleta); Maryland Emerging Infections Program, Baltimore, Maryland, USA (L. Wilson, E. Vaeth); New York–Rochester Emerging Infections Program, Rochester, New York, USA (G. Dumyati, C. Concannon); University of Rochester Medical Center, Rochester (G. Dumyati, C. Concannon); University of New Mexico, Albuquerque, New Mexico, USA (E.C. Phipps, K. Culbreath); Colorado Department of Public Health and Environment, Denver, Colorado, USA (S.J. Janelle, W.M. Bamberg)

Main Article

Table 5

Results, by organism tested, for select phenotype-based definitions used to identify carbapenemase producers among 307 carbapenem-resistant enterobacterial isolates from 6 US Emerging Infections Program sites, January 1, 2011–January 30, 2014*

Organism Definition no., result, no. isolates/no. total (%)†
2‡
 4§
 5¶
 4 plus MHT#
False-positive Selected false-negative False-positive Selected false-negative False-positive Selected false-negative False-positive Selected false-negative
Klebsiella spp. 15/111 (13.5) 14/111 (12.6) 31/111 (27.9) 1/111 (0.9) 11/111 (9.9) 14/111 (12.6) 3/111 (2.7) 1/111 (0.9)
Enterobacter spp. 42/102 (41.2) 0/102 68/102 (66.7) 0/102 26/102 (25.5) 0/102 30/102 (29.4) 0/102
Escherichia coli 25/94 (26.6) 1/94 (1.1) 70/94 (74.5) 1/94 (1.1) 20/94 (21.3) 3/94 (3.2) 3/94 (3.2) 1/94 (1.1)

*MHT, the modified Hodge test.
†False-positive isolates are those meeting the definition but not found to produce a carbapenemase. Selected false-negative isolates were selected on the basis of nonsuceptibility to >1 carbapenem not meeting the definition but found to produce a carbapenemase.
‡Definition 2 nonsusceptible to any carbapenem, excluding ertapenem, and resistant to all third-generation cephalosporins tested (pre-2015 Centers for Disease Control and Prevention carbapenem-resistant Enterobacteriaceae surveillance definition).
§Definition 4, resistant to any carbapenem. This definition obtained the lowest number of selected false-negatives.
¶Definition 5, resistant to any carbapenem, excluding ertapenem. This definition obtained the lowest number of false-positives among definitions with selected false-negatives of <10%.
#Definition 4 (resistant to any carbapenem) plus MHT (i.e., 2-step testing).

Main Article

Page created: August 12, 2015
Page updated: August 12, 2015
Page reviewed: August 12, 2015
The conclusions, findings, and opinions expressed by authors contributing to this journal do not necessarily reflect the official position of the U.S. Department of Health and Human Services, the Public Health Service, the Centers for Disease Control and Prevention, or the authors' affiliated institutions. Use of trade names is for identification only and does not imply endorsement by any of the groups named above.
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