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Identifying carriers of carbapenem-resistant Enterobactericeae harboring KPC (Klebsiella pneumoniae carbapenemase) or NDM (New Dehli metallo-beta-lactamase) genes
The Centers for Disease Control and Prevention recommends active surveillance to detect unrecognized colonized patients who may be a potential source for carbapenemase-resistant Enterobacteriaceae (CRE) transmission. Such surveillance testing may be focused in certain high-risk settings or patient groups (eg, ICUs, long-term acute care, patients transferred from areas or facilities with high CRE prevalence) or by infection control to investigate an outbreak. Nonsusceptibility to carbapenems in gram-negative bacilli by means of the enzyme KPC (Klebsiella pneumoniae carbapenemase) or NDM (New Dehli metallo-beta-lactamase) is becoming more common. The genes blaKPC and blaNDM encode KPC and NDM enzyme production, respectively. PCR is a sensitive, specific, and rapid means identifying patients colonized by CRE harboring blaKPC or blaNDM.
This PCR detects and differentiates blaKPC and blaNDM in surveillance specimens (perirectal/rectal swabs or stool). A positive KPC (Klebsiella pneumoniae carbapenemase) and/or NDM (New Dehli metallo-beta-lactamase) PCR indicates that the patient is colonized by carbapenemase-resistant Enterobacteriaceae harboring blaKPC and/or blaNDM, respectively.
A negative result indicates the absence of detectable DNA; however, false-negative results may occur due to inhibition of PCR, sequence variability underlying primers and probes, or the presence of the blaKPC or blaNDM genes in quantities less than the limit of detection of the assay.
This assay should be used for surveillance testing on perirectal/rectal swabs or stool specimens. Request KPNRP / KPC (blaKPC) and NDM (blaNDM) in Gram-Negative Bacilli, Molecular Detection, PCR if testing isolates from culture.
The performance of this assay was demonstrated by spiking perirectal swab and stool specimens (30 positive and 30 negative for each specimen type) with quantified heat-killed bacteria carrying blaNDM or blaKPC. The sensitivity and specificity in spiked stool specimens was 100% for both blaNDM and blaKPC; for perirectal swabs the sensitivity and specificity was 93% and 100%, respectively, for blaKPC and 100% and 100%, respectively, for blaNDM. The assay had the following limits of detection in perirectal swabs and stool, respectively: blaKPC, 9 and 90 CFU/microliter and blaNDM 1.9 and 1.9 CFU/microliter.
In addition, 33 rectal swab specimens previously characterized as containing isolates of KPC PCR-positive Enterobacteriaceae using the method of Lolans(1) were tested by the Mayo Clinic KPC and NDM PCR assay. There was complete agreement with the expected results.
1. Lolans K, Calvert K, Won S, et al: Direct ertapenem disk screening method for identification of KPC-producing Klebsiella pneumoniae and Escherichia coli in surveillance swab specimens J Clin Microbiol 2010;48:836-841
2. Cunningham SA, Noorie T, Meunier D, et al: Rapid and simultaneous detection of genes encoding Klebsiella pneumoniae carbapenemase (blaKPC) and New Delhi metallo-beta-lactamase (blaNDM) in Gram-negative bacilli. J Clin Microbiol 2013;51:66-69
3. New carbapenem-resistant Enterobacteriaceae warrant additional action by healthcare providers. Centers for Disease Control and Prevention Health Alert Network, February 14, 2013
4. Vasoo S, Cunningham SA, Kohner PC, et al: Comparison of a direct and broth-enriched PCR, HardyCHROM ESBL and the CDC method for detection of Klebsiella pneumoniae carbapenemase carriage in surveillance rectal swabs. Abstracts of the Ninth International Symposium on Antimicrobial Agents and Resistance, Kuala Lumpur, Malaysia, March 13-15, 2013