Assessing pure isolates of gram-negative bacilli for mechanism of carbapenem resistance
Real-Time Polymerase Chain Reaction (PCR) using LightCycler with Amplified Product Detection using Fluorescent Resonance Energy Transfer (FRET) Hybridization Probes
Varies
This assay is for testing of isolates of gram-negative bacilli. If testing directly from rectal or perirectal swabs is desired, order KPNDP / Klebsiella pneumoniae Carbapenemase (blaKPC) and New Delhi Metallo-beta-Lactamase (blaNDM) Surveillance, PCR, Varies.
1. For shipping information see Infectious Specimen Shipping Guidelines .
2. Place specimen in a large infectious container and label as an etiologic agent/infectious substance.
Organism identification and specimen source are required.
Question ID | Description | Answers |
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SRC53 | Specimen source |
The high sensitivity of amplification by polymerase chain reaction requires the specimen to be processed in an environment in which contamination of the specimen by Klebsiella pneumoniae or New Delhi metallo-beta-lactamase DNA is unlikely.
Supplies: Infectious Container, Large (T146)
Container/Tube: Slant
Specimen Volume: Isolate
Collection Instructions:
1. Isolate the bacteria.
2. Bacterial organism must be in pure culture, actively growing. Do not submit mixed cultures.
If not ordering electronically, complete, print, and send a Microbiology Test Request (T244) with the specimen.
Agar plate Mixed cultures | Reject |
Specimen Type | Temperature | Time | Special Container |
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Varies | Ambient (preferred) | ||
Refrigerated |
Assessing pure isolates of gram-negative bacilli for mechanism of carbapenem resistance
Nonsusceptibility to carbapenems in gram-negative bacilli by means of the enzyme KPC (Klebsiella pneumoniae carbapenemase) or NDM (New Delhi metallo-beta-lactamase) is becoming more common. The genes blaKPC and blaNDM encode KPC and NDM enzyme production, respectively. In addition to KPC and NDM production, there are other mechanisms of resistance to carbapenems in gram-negative bacilli, including production of other carbapenemases or plasmid-encoded AmpC, or extended beta-lactamase production combined with decreased membrane permeability. Detection of carbapenemases by the modified Hodge test may be subjective and is not rapid. Testing for the minimum inhibitory concentration determines the level but not the mechanism of resistance. Polymerase chain reaction testing is a sensitive, specific, and rapid means of detecting of a specific portion of the genes encoding KPC and NDM production.
Not applicable
This polymerase chain reaction (PCR) test detects and differentiates both blaKPC and blaNDM. A positive KPC (Klebsiella pneumoniae carbapenemase) PCR result indicates the isolate carries blaKPC. A positive NDM (New Delhi metallo-beta-lactamase) PCR result indicates the isolate carries blaNDM.
A negative result indicates the absence of detectable blaKPC or blaNDM DNA; however, false-negative results may occur due to inhibition of PCR, sequence variability underlying primers, or loss of a plasmid carrying blaKPC and blaNDM.
No significant cautionary statements
The assay was validated using 159 gram-negative bacillus isolates, including 135 carbapenemase-producers (105 blaNDM positive and 30 blaKPC positive). The assay had 100% sensitivity and specificity for isolate testing compared with reference methods, including the modified Hodge test, testing for blaKPC using KPC (Klebsiella pneumoniae carbapenemase) polymerase chain reaction (PCR) and testing for blaNDM by NDM (New Dehli metallo-beta-lactamase) PCR at the Health Protection Agency (HPA), London, UK.
1. Centers for Disease Control and Prevention, National Center for Emerging and Zoonotic Infectious Diseases (NCEZID), Division of Healthcare Quality Promotion (DHQP): Multiplex real-time PCR detection of Klebsiella pneumoniae carbapenemase (KPC) and New Delhi metallo-beta-lactamase (NDM-1) genes. CDC; 2011. Accessed February 14, 2023. Available at www.cdc.gov/hai/settings/lab/kpc-ndm1-lab-protocol.html
2. Clinical Laboratory Standards Institute (CLSI): Performance Standards for Antimicrobial Susceptability Testing. 32nd ed. CLSI Document M100. CLSI; 2022
3. Centers for Disease Control and Prevention: New carbapenem-resistant Enterobacteriaceae warrant additional action by healthcare providers. CDC; February 14, 2013. Accessed February 14, 2023. Available at https://stacks.cdc.gov/view/cdc/25250
4. Bialvaei AZ, Kafil HS, Asgharzadeh M, Yousef Memar M, Yousefi M: Current methods for the identification of carbapenemases. J Chemother. 2016;28(1):1-19
Isolates are lysed in buffer to release their DNA. This assay amplifies and detects a specific portion of the genes encoding the KPC (Klebsiella pneumoniae carbapenemase) and NDM (New Delhi metallo-beta-lactamase) enzymes. The LightCycler instrument amplifies and monitors target nucleic acid sequences by fluorescence during polymerase chain reaction (PCR) cycling. This is an automated PCR system that can rapidly detect amplified product development through stringent air-controlled temperature cycling and capillary cuvettes. The detection of amplified products is based on the fluorescent-resonance energy transfer (FRET) principle. For FRET product detection, a hybridization probe with a donor fluorophore, fluorescein, on the 3' end is excited by an external light source, which emits light that is absorbed by a second hybridization probed with an acceptor fluorophore LC-Led 610 (blaKPC specific) and LC-red 670 (blaNDM specific), on the 5' end. The acceptor fluorophore then emits a light of a different wavelength that can be measured with a signal that is proportional to the amount of specific PCR product. The detection process is completed in less than 1 hour using a closed tube system.(Cunningham SA, Noorie T, Meunier D, Woodford N, Patel R. Rapid and simultaneous detection of genes encoding Klebsiella pneumoniae carbapenemase (blaKPC) and New Delhi metallo-ß-lactamase (blaNDM) in Gram-negative bacilli. J Clin Microbiol. 2013 Apr;51(4):1269-71. doi: 10.1128/JCM.03062-12. Erratum in: J Clin Microbiol. 2013 Oct;51(10):3472)
Monday through Friday
This test was developed, and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.
87150 x2
Test Id | Test Order Name | Order LOINC Value |
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KPNRP | KPC and NDM PCR | 85502-3 |
Result Id | Test Result Name |
Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
|
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SRC53 | Specimen source | 31208-2 |
35168 | KPC PCR | 49617-4 |
35169 | NDM PCR | 73982-1 |