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J Clin Microbiol. 2015 Jun;53(6):1812-22. doi: 10.1128/JCM.03506-14. Epub 2015 Mar 11.

A statistical approach for determination of disk diffusion-based cutoff values for systematic characterization of wild-type and non-wild-type bacterial populations in antimicrobial susceptibility testing.

Author information

1
Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland.
2
Epidemiology, Biostatistics and Prevention Institute, University of Zurich, Zurich, Switzerland.
3
Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland mhombach@imm.uzh.ch.

Abstract

In this study, we introduce a new approach for determination of epidemiologic cutoffs (ECOFFs) and resistant-population cutoffs (RCOFFs) based on receiver operating characteristic (ROC) curves. As an example, the method was applied for determination of ECOFFs for seven different beta-lactam antibiotics and wild-type populations of Escherichia coli, Klebsiella pneumoniae, and Enterobacter cloacae. In addition, RCOFFs were determined for bacterial populations with defined resistance mechanisms ("resistotypes"), i.e., extended-spectrum beta-lactamase (ESBL)-positive E. coli, ESBL-positive K. pneumoniae, and ESBL-positive E. cloacae; AmpC cephalosporinase-positive E. coli and AmpC-positive K. pneumoniae; and broad-spectrum beta-lactamase (BSBL)-positive E. coli. RCOFFs and ECOFFs are instrumental for a systematic characterization of associations between resistotypes and wild-type populations.

PMID:
25762772
PMCID:
PMC4432064
DOI:
10.1128/JCM.03506-14
[Indexed for MEDLINE]
Free PMC Article

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