title: Use of faropenem as an indicator of carbapenemase activity in the Enterobacteriaceae.
abstract: The aim of this study was to determine the ability of a disc susceptibility test using faropenem (10 μg) to predict carbapenemase activity in Enterobacteriaceae. A collection of 166 isolates of carbapenemase-producing Enterobacteriaceae (CPE) and 82 isolates of Enterobacteriaceae that produced other β-lactamases was compiled from diverse sources. Disc susceptibility testing was performed using the CLSI/EUCAST methodology with discs of faropenem (10 μg), temocillin (30 μg), and four carbapenems (each 10 μg). A further prospective evaluation of the faropenem disc susceptibility test was performed using 205 consecutive isolates referred to a United Kingdom reference laboratory in parallel with molecular methods for carbapenemase detection. Of 166 isolates of CPE, 99% showed growth up to the edge of a 10-μg faropenem disc compared with only 6% of other β-lactamase producers (sensitivity, 99%; specificity, 94%). A "double zone" around 10-μg faropenem discs was frequently associated with OXA-48 producers. Of the carbapenems, the most useful agent was imipenem, where a zone diameter of ≤ 23 mm as a predictor of carbapenemase activity had a sensitivity of 99% and a specificity of 85%. The presence of no zone of inhibition around a 30-μg temocillin disc was a consistent feature of strains producing OXA-48 carbapenemase. For 205 isolates of Enterobacteriaceae referred to a United Kingdom reference laboratory, growth up to a 10-μg faropenem disc correctly identified 84 of 86 carbapenemase producers (98% sensitivity), with a specificity of 87%. Disc susceptibility testing using faropenem (10 μg) is a simple, convenient, and highly predictive screening test for carbapenemase-producing Enterobacteriaceae.
authors.affiliation: Microbiology Department, Freeman Hospital, Newcastle upon Tyne, United Kingdom.
authors.forename: Kathryn M
authors.initials: KM
authors.lastname: Day
authors.forename: Rachel
authors.initials: R
authors.lastname: Pike
authors.forename: Trevor G
authors.initials: TG
authors.lastname: Winstanley
authors.forename: Clare
authors.initials: C
authors.lastname: Lanyon
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Cummings
authors.forename: Muhammad W
authors.initials: MW
authors.lastname: Raza
authors.forename: Neil
authors.initials: N
authors.lastname: Woodford
authors.forename: John D
authors.initials: JD
authors.lastname: Perry
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000378:metabolism*; D004755:Enterobacteriaceae / Q000187:drug effects* / Q000201:enzymology* / Q000302:isolation & purification / Q000378:metabolism; D004756:Enterobacteriaceae Infections / Q000382:microbiology; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods; D012680:Sensitivity and Specificity; D006113:United Kingdom; D001618:beta-Lactamases / Q000378:metabolism*; D047090:beta-Lactams / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D047090:beta-Lactams; D001618:beta-Lactamases; C063912:carbapenemase; C107057:fropenem