title: Utilizing the Carba NP test as an indicator of expression level of carbapenemase genes in Enterobacteriaceae.
abstract: The Carba NP test was developed to detect carbapenemase-producing Enterobacteriaceae, and uses imipenem as the reaction substrate. In Japan, IMP-6 metallo-β-lactamase (MBL) producers, which are usually resistant to meropenem but susceptible to imipenem, and IMP-1 MBL producers, which are usually resistant to both carbapenems are prevalent. We performed the Carba NP test with IMP-6 and IMP-1 MBL producers, and both types were detected by the Carba NP test with high sensitivity. All IMP-1 MBL producers were detected by the Carba NP test, but the minimum inhibitory concentrations (MICs) of imipenem varied from 0.25 to >32μg/mL, and the time to positivity varied from 0 to 30min. Time to positivity was significantly correlated with expression levels of blaIMP-1, but not with MICs of imipenem. These results suggested that the Carba NP test can be used as a screening assay for carbapenemase gene expression levels among producers of the same type of carbapenemase. Using this approach, it is possible to determine whether the carbapenem resistance of each carbapenemase-producing Enterobacteriaceae isolate is primarily due to carbapenemase production, or to another mechanism such as outer membrane impermeability.
authors.affiliation: Department of Bacteriology II, National Institute of Infectious Diseases, Musashimurayama, Tokyo, Japan.
authors.forename: Takaya
authors.initials: T
authors.lastname: Segawa
authors.affiliation: Department of Bacteriology II, National Institute of Infectious Diseases, Musashimurayama, Tokyo, Japan.
authors.forename: Mari
authors.initials: M
authors.lastname: Matsui
authors.affiliation: Department of Bacteriology II, National Institute of Infectious Diseases, Musashimurayama, Tokyo, Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Suzuki
authors.affiliation: Department of Bacteriology II, National Institute of Infectious Diseases, Musashimurayama, Tokyo, Japan.
authors.forename: Atsuko
authors.initials: A
authors.lastname: Tsutsui
authors.affiliation: Pathogen Genomics Center, National Institute of Infectious Diseases, Shinjyuku-ku, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Kuroda
authors.affiliation: Department of Bacteriology II, National Institute of Infectious Diseases, Musashimurayama, Tokyo, Japan.
authors.forename: Keigo
authors.initials: K
authors.lastname: Shibayama
authors.affiliation: Department of Bacteriology II, National Institute of Infectious Diseases, Musashimurayama, Tokyo, Japan. Electronic address: suzukiss@nih.go.jp.
authors.forename: Satowa
authors.initials: S
authors.lastname: Suzuki
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001431:Bacteriological Techniques / Q000379:methods*; D024881:Drug Resistance, Bacterial; D004755:Enterobacteriaceae / Q000201:enzymology* / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D015971:Gene Expression Regulation, Enzymologic; D015378:Imipenem / Q000737:chemistry / Q000494:pharmacology; D007564:Japan; D000077731:Meropenem; D008826:Microbial Sensitivity Tests; D013845:Thienamycins / Q000737:chemistry / Q000494:pharmacology; D001618:beta-Lactamases / Q000235:genetics* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D013845:Thienamycins; D015378:Imipenem; C409201:beta-lactamase IMP-1; D001618:beta-Lactamases; C063912:carbapenemase; D000077731:Meropenem
keywords: Carba NP test; Carbapenemase gene expression; Carbapenemase-producing Enterobacteriaceae; IMP type metallo-β-lactamase