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The KPC/NDM/OXA-48 carbapenemase (qPCR) product is used to determine the sequences of genes encoding KPC, NDM, and OXA-48 carbapenemases in DNA preparations obtained from human material.
Kit size: 100 markers
Reaction: fourplex (FAM: KPC carbapenemases, HEX: internal control, Texas Red: NDM carbapenemases, Cy5: OXA-48 carbapenemases)
Internal control: exogenous/endogenous
Determination: qualitative/quantitative
Kit components:
The most common mechanism of resistance of Enterobacterales to carbapenems is the production of carbapenemases, which mainly include KPC, NDM, VIM, IMP, and OXA-48-like. Most of them are encoded on plasmids. Therefore, carbapenem resistance genes spread easily through horizontal gene transfer. Another less common mechanism of carbapenem resistance is the combination of extended-spectrum beta-lactamase (ESBL) or AmpC expression and porin loss or overexpression of efflux pumps.
Carbapenem-resistant Enterobacterales (CRE) resulting from the first mechanism are referred to as carbapenemase-producing CRE (CP-CRE). Carbapenem-resistant Enterobacterales resulting from the second mechanism are referred to as non-carbapenemase-producing CRE (non-CP-CRE).
All three types of carbapenemases belong to β-lactamases classified as class A, B, and D, respectively. Class A is the largest category of β-lactamases in terms of the number of types and variants. KPC-type enzymes are by far the most clinically and epidemiologically significant in this class. Class B β-lactamases, to which NDM belongs, represent the most distinct evolutionary and structural lineage of these enzymes, and their functional specificity is most notable for their dependence on zinc ions and their natural ability to hydrolyze carbapenems. Class D is the most diverse category of β-lactamases in terms of evolution and structure, and since most of these enzymes hydrolyze isoxazolyl penicillins (oxacillin and cloxacillin) best, they are commonly referred to as oxacillinases (OXA).
KPC enzymes are one of the three most common types of carbapenemases in Enterobacterales. The first strain producing KPC carbapenemase (KPC-2) was isolated in the USA in 1996. The name “KPC” was taken from the species Klebsiella pneumoniae (Klebsiella pneumoniae carbapenemase), and although these enzymes were soon identified in other Enterobacterales and, over time, in other Gram-negative bacteria, K. pneumoniae remains their dominant producer. The activity of KPC β-lactamases covers virtually all classic types of β-lactams, i.e., penicillins, first- to fourth-generation cephalosporins, monobactams, and carbapenems. The only weak substrates among them are cefoxitin and ceftazidime.
Several groups of carbapenemases are recommended for class B β-lactamases (MBL): NMD, IMP, and VIM. The substrate spectrum of the vast majority of class B β-lactamases is extensive and also includes penicillins and first- to fourth-generation cephalosporins, and the only group of classic β-lactams that are by definition not hydrolyzed are monobactams, i.e., aztreonam. MBLs are not inhibited by β-lactam inhibitors such as clavulanate, sulbactam, and tazobactam. Among the recently introduced new fifth-generation cephalosporins, only cefiderocol shows in vitro activity against MBL strains.
The first member of the NDM group of carbapenemases was first identified in 2008 in a Klebsiella pneumoniae isolate taken from a Swedish patient hospitalized in India. The name of this group of enzymes derives from the place of its discovery: NDM, New Delhi metallo-β-lactamase.
OXA-type carbapenemases belong to class D β-lactamases. Enzymes from this group are also referred to as CHDL carbapenemases (carbapenem-hydrolyzing Class D β-lactamases). CHDL carbapenemases have been identified as enzymes specific to certain microorganisms. These are primarily species of the genera Acinetobacter, Shewanella, and Aeromonas.
The most important CHDLs in Enterobacterales are definitely the OXA-48 enzymes, especially their first known variant, which gave its name to the entire family. The first K. pneumoniae strain producing OXA-48 was isolated in Turkey in 2001. Shortly thereafter, reports appeared of the identification of this enzyme in isolates of various Enterobacterales species. In most cases, these were species of K. pneumoniae, E. coli, and the E. cloacae complex collected from various geographical areas, such as Turkey, North African countries, and Western Europe.
