title: Carbapenem resistance in Klebsiella pneumoniae not detected by automated susceptibility testing.
abstract: Detecting beta-lactamase-mediated carbapenem resistance among Klebsiella pneumoniae isolates and other Enterobacteriaceae is an emerging problem. In this study, 15 blaKPC-positive Klebsiella pneumoniae that showed discrepant results for imipenem and meropenem from 4 New York City hospitals were characterized by isoelectric focusing; broth microdilution (BMD); disk diffusion (DD); and MicroScan, Phoenix, Sensititre, VITEK, and VITEK 2 automated systems. All 15 isolates were either intermediate or resistant to imipenem and meropenem by BMD; 1 was susceptible to imipenem by DD. MicroScan and Phoenix reported 1 (6.7%) and 2 (13.3%) isolates, respectively, as imipenem susceptible. VITEK and VITEK 2 reported 10 (67%) and 5 (33%) isolates, respectively, as imipenem susceptible. By Sensititre, 13 (87%) isolates were susceptible to imipenem, and 12 (80%) were susceptible to meropenem. The VITEK 2 Advanced Expert System changed 2 imipenem MIC results from >16 ?g/mL to <2 ?g/mL but kept the interpretation as resistant. The recognition of carbapenem-resistant K. pneumoniae continues to challenge automated susceptibility systems.
authors.affiliation: Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention, 1600 Clifton Road, Atlanta, GA 30333, USA. fnt1@cdc.gov
authors.forename: Fred C
authors.initials: FC
authors.lastname: Tenover
authors.forename: Rajinder K
authors.initials: RK
authors.lastname: Kalsi
authors.forename: Portia P
authors.initials: PP
authors.lastname: Williams
authors.forename: Roberta B
authors.initials: RB
authors.lastname: Carey
authors.forename: Sheila
authors.initials: S
authors.lastname: Stocker
authors.forename: David
authors.initials: D
authors.lastname: Lonsway
authors.forename: J Kamile
authors.initials: JK
authors.lastname: Rasheed
authors.forename: James W
authors.initials: JW
authors.lastname: Biddle
authors.forename: John E
authors.initials: JE
authors.lastname: McGowan
authors.forename: Bruce
authors.initials: B
authors.lastname: Hanna
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001331:Automation; D015780:Carbapenems / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D006801:Humans; D015378:Imipenem / Q000494:pharmacology; D007711:Klebsiella pneumoniae / Q000187:drug effects*; D000077731:Meropenem; D008826:Microbial Sensitivity Tests / Q000295:instrumentation / Q000379:methods; D012015:Reference Standards; D013845:Thienamycins / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D015780:Carbapenems; D013845:Thienamycins; D015378:Imipenem; D000077731:Meropenem