title: 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.
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.
authors.affiliation: Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland.
authors.forename: Giorgia
authors.initials: G
authors.lastname: Valsesia
authors.affiliation: Epidemiology, Biostatistics and Prevention Institute, University of Zurich, Zurich, Switzerland.
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Roos
authors.affiliation: Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland.
authors.forename: Erik C
authors.initials: EC
authors.lastname: Böttger
authors.affiliation: Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland mhombach@imm.uzh.ch.
authors.forename: Michael
authors.initials: M
authors.lastname: Hombach
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D019540:Area Under Curve; D001419:Bacteria / Q000187:drug effects*; D001424:Bacterial Infections / Q000175:diagnosis / Q000382:microbiology*; D052978:Disk Diffusion Antimicrobial Tests / Q000379:methods / Q000592:standards*; D006801:Humans; D012016:Reference Values
chemical_list: D000900:Anti-Bacterial Agents