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The OXA-23/OXA-40/OXA-58 carbapenemase (qPCR) product is used to determine the sequence of genes encoding OXA carbapenemases from the OXA-23, OXA-40, and OXA-58 groups in DNA preparations obtained from human material.
Kit size: 100 markers
Reaction: fourplex (FAM: OXA-23 group carbapenemases, HEX: internal control, Texas Red: OXA-40 group carbapenemases, Cy5: OXA-58 group 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).
OXA carbapenemases are among the earliest detected β-lactamases classified as class D. Their name derives from their ability to hydrolyze oxacillin and cloxacillin. Class D β-lactamases were originally relatively rare. Their substrate profile was limited to penicillins, but some of them also confer resistance to cephalosporins. OXA-23, OXA-40, and OXA-58 carbapenemases were discovered in the 1980s in carbapenem-resistant Acinetobacter baumannii isolates. Over time, the genes encoding these types of carbapenemases migrated to Enterobacteriaceae and gradually became an important cause of carbapenem resistance in this taxonomic group.
The OXA-23 group was the first carbapenem-resistant lactamase group identified in Acinetobacter baumannii. The OXA-23 lactamase was first identified in an A. baumannii isolate collected in Edinburgh, UK, in 1985. The sequence of the blaOXA-23 gene was published in 2000. Since then, 18 alleles of this gene encoding OXA-23 lactamases have been identified. The genes of this enzyme group are often carried by plasmids. They have been found in many Acinetobacter species, as well as in species belonging to Enterobacteriaceae. The discovery of several blaOXA-23-like genes on the chromosome of Acinetobacter radioresistens isolates indicates that this species is a likely natural source of this enzyme group.
The OXA-40 group is the second OXA-type lactamase group identified in Acinetobacter baumannii. The founding member of this group, OXA-24, later renamed OXA-40, was identified in isolates in 1997 that were part of an outbreak in Spain. Since then, six additional variants of the enzyme have been discovered. The latest data indicate the presence of genes encoding OXA-40 on plasmids in other Acinetobacter species, as well as in P. aeruginosa and Klebsiella pneumonia.
The first member of the OXA-58 enzyme group was identified in France in 2003. It was found in a multidrug-resistant clinical isolate of A. baumannii, which also exhibited resistance to carbapenems. OXA-58 carbapenemases have properties similar to those found in other OXA-type enzymes in A. baumannii. They show weak activity against carbapenems and penicillin and have the ability to hydrolyze cefpirome and cephalothin.
