Detection of Klebsiella pneumoniae Carbapenemase (KPC) Production in Non-Klebsiella pneumoniae Enterobacteriaceae Isolates by Use of the Phoenix, Vitek 2, and Disk Diffusion Methods

Department of Pathology, University of Texas Southwestern Medical Center, Dallas, Texas 75235, USA.
Journal of clinical microbiology (Impact Factor: 3.99). 03/2011; 49(3):1143-7. DOI: 10.1128/JCM.02163-10
Source: PubMed


In this study, we tested the abilities of the Vitek 2, BD Phoenix, and Kirby Bauer disk diffusion tests to detect carbapenemase
production in a collection of 14 Klebsiella pneumoniae carbapenemase (KPC)-producing non-Klebsiella pneumoniae isolates. In addition, we evaluated 13 KPC-positive K. pneumoniae isolates by using each of these methods and applied both 2009 and 2010 CLSI carbapenem interpretive guidelines.

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    • "However, detection of KPC -harboring stains in the clinical laboratory remained a difficult task. The failure of automated susceptibility testing systems to detect KPC-mediated carbapenems resistance was previously reported [12-14]. In 2009, the Clinical Laboratory Standards Institute (CLSI) guidelines (M100) recommended MHT to detect carbapenemase production. "
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    ABSTRACT: Klebsiella pneumonia carbapenemases (KPCs) are able to hydrolyze the carbapenems, which cause many bacteria resistance to multiple classes of antibiotics, so the rapid dissemination of KPCs is worrisome. Laboratory identification of KPCs-harboring clinical isolates would be a key to limit the spread of the bacteria. This study would evaluate a rapid low-cost real-time PCR assay to detect KPCs. Real-time PCR assay based on SYBR GreenIwas designed to amplify a 106 bp product of the blaKPC gene from the 159 clinical Gram-negative isolates resistant to several classes of -lactam antibiotics through antimicrobial susceptibility testing. We confirmed the results of real-time PCR assay by the conventional PCR-sequencing. At the same time, KPCs of these clinical isolates were detected by the modified Hodge test (MHT). Then we compared the results of real-time PCR assay with those of MHT from the sensitivity and specificity. Moreover, we evaluated the sensitivity of the real-time PCR assay. The sensitivity and specificity of the results of the real-time PCR assay compared with those of MHT was 29/29(100%) and 130/130(100%), respectively. The results of the real-time PCR and the MHT were strongly consistent (Exact Sig. (2-tailed) =1. 000; McNemar test). The real-time PCR detection limit was about 0.8 cfu using clinical isolates. The real-time PCR assay could rapidly and accurately detect KPCs -harboring strains with high analytical sensitivity and specificity.
    Full-text · Article · Apr 2012 · Annals of Clinical Microbiology and Antimicrobials
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    ABSTRACT: The accurate phenotypic detection of Klebsiella pneumoniae carbapenemase (KPC)-producing Enterobacteriaceae is an increasing necessity worldwide. We evaluated the performance of boronic acid combined-disk tests using as substrate imipenem or meropenem and as inhibitor of KPC production 300 μg aminophenylboronic acid (APBA), 600 μg APBA, or 400 μg phenylboronic acid (PBA). Tests were considered positive when an increase in the growth-inhibitory zone around a carbapenem disk with KPC inhibitor was 5 mm or greater of the growth-inhibitory zone diameter around the disk containing carbapenem alone. The comparison of the combined-disk tests was performed with 112 genotypically confirmed KPC-possessing Enterobacteriaceae isolates. To measure the specificity of the tests, 127 genotypically confirmed KPC-negative Enterobacteriaceae isolates that were nonsusceptible to at least one carbapenem were chosen for testing. Using disks containing imipenem without and with 300 μg APBA, 600 μg APBA, or 400 μg PBA, 72, 92, and 112 of the KPC producers, respectively, gave positive results (sensitivities, 64.3%, 82.1%, and 100%, respectively). Using disks containing meropenem without and with 300 μg APBA, 600 μg APBA, or 400 μg PBA, 87, 108, and 112 of the KPC producers, respectively, gave positive results (sensitivities, 77.7%, 96.4%, and 100%, respectively). Among KPC producers, the disk potentiation tests using meropenem and PBA demonstrated the largest differences in inhibition zones (P < 0.001). All combined-disk tests correctly identified 124 of the 127 non-KPC producers (specificity, 97.6%). This comparative study showed that PBA is the most effective inhibitor of KPC enzymes, and its use in combined-disk tests with meropenem may give the most easily interpreted results.
    Full-text · Article · Jun 2011 · Journal of clinical microbiology
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    ABSTRACT: Using the updated 2010 CLSI carbapenem breakpoints for the Enterobacteriaceae, nonsusceptibility to ertapenem and imipenem predicted the presence of blaKPC poorly, especially among Escherichia coli and Enterobacter species. In regions where KPC-producing bacteria are endemic, testing for nonsusceptibility to meropenem may provide improved accuracy in identifying these isolates.
    Preview · Article · Aug 2011 · Journal of clinical microbiology
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