title: Discordance in the minimal inhibitory concentrations of ertapenem for Enterobacter cloacae: Vitek 2 system versus Etest and agar dilution methods.
abstract: Our objective was to compare the ertapenem minimal inhibitory concentrations (MICs) for Enterobacter cloacae isolates categorized intermediate or resistant to ertapenem when measured with the Vitek 2 system, with the MICs for these isolates when measured by two methods performed in agar medium: the Etest and agar plate dilution method (APDM). Overall, 50 E. cloacae isolates were included in the study. The mean MIC of ertapenem was 2.92±1.77μg/ml according to the Vitek 2 system, 0.94±0.84μg/ml according to the Etest strips, and 0.93±0.62μg/ml according to the APDM. Furthermore, the MICs determined by the Vitek 2 system were higher than the MICs determined by the two other methods for 96% of strains. Lastly, according to the Etest strips and APDM, 42% of E. cloacae were susceptible to ertapenem. No carbapenemase was identified by the screening method used. Using the Vitek 2 system to determine ertapenem MICs for E. cloacae can have potential consequences in terms of additional carbapenemase-detecting tests and antimicrobial therapy. It would be interesting to determine if the Vitek 2 system is more effective for the detection of carbapenemase producers with low-level carbapenem resistance than the two methods performed in agar medium.
authors.affiliation: Laboratoire de Bactériologie, Centre Hospitalier Universitaire, 4 rue Larrey, Angers, France.
authors.forename: Hélène
authors.initials: H
authors.lastname: Pailhoriès
authors.affiliation: Laboratoire de Bactériologie, Centre Hospitalier Universitaire, 4 rue Larrey, Angers, France; Groupe d'Etude des Interactions Hôtes Pathogènes (GEIHP, EA 3127), UFR Médecine, Université d'Angers, rue Haute de Reculée, Angers, France.
authors.forename: Viviane
authors.initials: V
authors.lastname: Cassisa
authors.affiliation: Laboratoire de Bactériologie, Centre Hospitalier Universitaire, 4 rue Larrey, Angers, France.
authors.forename: Claudie
authors.initials: C
authors.lastname: Lamoureux
authors.affiliation: Laboratoire de Bactériologie, Centre Hospitalier Universitaire, 4 rue Larrey, Angers, France.
authors.forename: Adélaïde
authors.initials: A
authors.lastname: Chesnay
authors.affiliation: Laboratoire de Bactériologie, Centre Hospitalier Universitaire, 4 rue Larrey, Angers, France.
authors.forename: Cyrielle
authors.initials: C
authors.lastname: Lebreton
authors.affiliation: Laboratoire de Bactériologie, Centre Hospitalier Universitaire, 4 rue Larrey, Angers, France.
authors.forename: Carole
authors.initials: C
authors.lastname: Lemarié
authors.affiliation: Laboratoire de Bactériologie, Centre Hospitalier Universitaire, 4 rue Larrey, Angers, France; Groupe d'Etude des Interactions Hôtes Pathogènes (GEIHP, EA 3127), UFR Médecine, Université d'Angers, rue Haute de Reculée, Angers, France.
authors.forename: Marie
authors.initials: M
authors.lastname: Kempf
authors.affiliation: Laboratoire de Bactériologie, Centre Hospitalier Universitaire, 4 rue Larrey, Angers, France.
authors.forename: Chetaou
authors.initials: C
authors.lastname: Mahaza
authors.affiliation: Laboratoire de Bactériologie, Centre Hospitalier Universitaire, 4 rue Larrey, Angers, France; Groupe d'Etude des Interactions Hôtes Pathogènes (GEIHP, EA 3127), UFR Médecine, Université d'Angers, rue Haute de Reculée, Angers, France.
authors.forename: Marie-Laure
authors.initials: ML
authors.lastname: Joly-Guillou
authors.affiliation: Laboratoire de Bactériologie, Centre Hospitalier Universitaire, 4 rue Larrey, Angers, France; Groupe d'Etude des Interactions Hôtes Pathogènes (GEIHP, EA 3127), UFR Médecine, Université d'Angers, rue Haute de Reculée, Angers, France. Electronic address: MaEveillard@chu-angers.fr.
authors.forename: Matthieu
authors.initials: M
authors.lastname: Eveillard
mesh_terms: D000362:Agar / Q000737:chemistry; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000378:metabolism; D003470:Culture Media; D024881:Drug Resistance, Bacterial; D016972:Enterobacter cloacae / Q000187:drug effects* / Q000302:isolation & purification; D000077727:Ertapenem; D004926:Escherichia coli / Q000187:drug effects; D008826:Microbial Sensitivity Tests / Q000379:methods*; D001618:beta-Lactamases / Q000378:metabolism; D047090:beta-Lactams / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D003470:Culture Media; D047090:beta-Lactams; D000362:Agar; D001618:beta-Lactamases; C063912:carbapenemase; D000077727:Ertapenem
keywords: Enterobacter; Ertapenem; Minimal inhibitory concentration