title: The Resistant-Population Cutoff (RCOFF): a New Concept for Improved Characterization of Antimicrobial Susceptibility Patterns of Non-Wild-Type Bacterial Populations.
abstract: This study aimed to determine resistant-population cutoffs (RCOFFs) to allow for improved characterization of antimicrobial susceptibility patterns in bacterial populations. RCOFFs can complement epidemiological cutoff (ECOFF)-based settings of clinical breakpoints (CBPs) by systematically describing the correlation between non-wild-type and wild-type populations. We illustrate this concept by describing three paradigmatic examples of wild-type and non-wild-type Escherichia coli populations from our clinical strain database of disk diffusion diameters. The statistical determination of RCOFFs and ECOFFs and their standardized applications in antimicrobial susceptibility testing (AST) facilitates the assignment of isolates to wild-type or non-wild-type populations. This should improve the correlation of in vitro AST data and distinct antibiotic resistance mechanisms with clinical outcome facilitating the setting and validation of CBPs.
authors.affiliation: Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland.
authors.forename: Giorgia
authors.initials: G
authors.lastname: Valsesia
authors.affiliation: Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Hombach
authors.affiliation: Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland.
authors.forename: Florian P
authors.initials: FP
authors.lastname: Maurer
authors.affiliation: Unité des Agents Antibactériens, Institut Pasteur, Paris, France.
authors.forename: Patrice
authors.initials: P
authors.lastname: Courvalin
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 boettger@imm.uzh.ch.
authors.forename: Erik C
authors.initials: EC
authors.lastname: Böttger
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D004926:Escherichia coli / Q000187:drug effects; D004927:Escherichia coli Infections / Q000382:microbiology; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000592:standards*; D012016:Reference Values; D015203:Reproducibility of Results
chemical_list: D000900:Anti-Bacterial Agents