title: Towards a phenotypic screening strategy for emerging β-lactamases in Gram-negative bacilli.
abstract: The purpose of this manuscript was to review recent literature and guidelines regarding phenotypic detection of emerging β-lactamases [extended-spectrum β-lactamases (ESBLs), AmpC β-lactamases and carbapenemases] in Gram-negative bacilli (GNB) in order to formulate recommendations on best practice to screen for them. We conclude that chromogenic ESBL screening agar plates are suitable to screen for ESBL-producing Enterobacteriaceae directly from clinical samples. Furthermore, ceftazidime (CAZ) and ceftriaxone or cefotaxime (CTX) are the indicator antimicrobial agents of choice for ESBL detection in GNB. In non-inducible Enterobacteriaceae, the combined double-disk synergy test (CDDST) with at least CTX and CAZ and additionally cefepime as indicators is the preferred ESBL confirmation assay. The two most suitable ESBL confirmation strategies in AmpC co-producing Enterobacteriaceae are adapted CDDSTs: (i) with addition of 3-aminophenylboronic acid to CTX and CAZ disks; and (ii) with addition of cloxacillin (CLOX) to Mueller-Hinton agar. Reduced cefoxitin susceptibility and decreased susceptibility to cefotetan are regarded as suitable screening tests for plasmid-mediated and derepressed AmpC production. A CLOX-based CDDST with CTX and CAZ as indicators is considered to be the best AmpC confirmation assay. Finally, in Enterobacteriaceae isolates we suggest to screen for carbapenemases with a 0.5 μg/mL meropenem screening breakpoint. For class A carbapenemase confirmation, the home-prepared as well as the commercially available boronic acid-based CDDST can be considered. For metallo-β-lactamase confirmation, ethylene diamine tetra-acetic-acid-based home-prepared assays are recommended. The most suitable method (CDDST or DDST) and indicator antimicrobial agent(s) vary depending on the bacterial genus.
authors.affiliation: Department of Clinical Microbiology, University Hospital Leuven, Herestraat 49, 3000 Leuven, Belgium.
authors.forename: Elise
authors.initials: E
authors.lastname: Willems
authors.forename: Jan
authors.initials: J
authors.lastname: Verhaegen
authors.forename: Koen
authors.initials: K
authors.lastname: Magerman
authors.forename: Sita
authors.initials: S
authors.lastname: Nys
authors.forename: Reinoud
authors.initials: R
authors.lastname: Cartuyvels
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D004755:Enterobacteriaceae / Q000187:drug effects* / Q000201:enzymology*; D004756:Enterobacteriaceae Infections / Q000382:microbiology; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods*; D018440:beta-Lactam Resistance; D001618:beta-Lactamases / Q000378:metabolism*; D047090:beta-Lactams / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D047090:beta-Lactams; D001618:beta-Lactamases