Evaluation of the EasyScreen™ ESBL/CPO Detection Kit for the Detection of β-Lactam Resistance Genes

Early detection of multidrug resistant bacteria is of paramount importance for implementing appropriate infection control strategies and proper antibacterial therapies. We have evaluated a novel real-time PCR assay using fluorescent probes and 3base (R) technology, the EasyScreen (TM) ESBL/CPO Detection Kit (Genetic Signatures, Newtown, Australia), for the detection of 15 beta-lactamase genes (bla(VIM), bla(NDM), bla(IMP), bla(OXA-48), bla(KPC), bla(OXA23), bla(OXA-51), bla(SME), bla(IMI), bla(GES), bla(TEM), bla(SHV), bla(CTX-M), bla(CMY), bla(DHA)) and colistin resistance mcr-1 gene from 341 bacterial isolates (219 Enterobacterales, 66 P. aeruginosa and 56 A. baumannii) that were grown on Mueller-Hinton (MH) agar plates. One colony was suspended in provided extraction buffer, which lyses and converts the nucleic acids into a 3base (R)-DNA form (cytosines are converted into uracil, and subsequently thymine during PCR). The converted bacterial DNA is then added to the 6 PCR mixes, with primers for three targets plus one internal control. The EasyScreen (TM) ESBL/CPO Detection Kit was able to detect the 5-major (NDM, VIM, IMP, KPC, OXA-48) and 2-minor (IMI, Sme) carbapenemases and their variants irrespective of the species expressing them with nearly 100% sensitivity and specificity. With cephalosporinases CMY (82% of sensitivity) and DHA (87% of sensitivity) detection of chromosomally encoded variants was less efficient. Similarly, the chromosomally encoded OXA-51 variants were not consistently detected in A. baumannii. Despite being capable of efficiently detecting bla(CTX-M-), bla(TEM-), bla(SHV-) and bla(GES)-like genes, the EasyScreen (TM) ESBL/CPO Detection Kit was not able to distinguish between penicillinases and ESBL-variants of TEM and SHV and between GES-ESBLs and GES-carbapenemases. As GES enzymes are still rare, their detection as an ESBL or a carbapenemase remains important. Detection of mcr-1 was efficient, but none of the other mcr-alleles were detected in the 341 bacterial isolates tested. The EasyScreen (TM) ESBL/CPO Detection Kit is adapted for the detection of the most prevalent carbapenemases encountered in Gram-negatives isolated worldwide.

Automated summary

Early detection of multidrug resistant bacteria is crucial for infection control and proper treatment. The EasyScreen(TM) ESBL/CPO Detection Kit is a highly efficient real-time PCR assay for detecting colistin resistance and beta-lactamase genes.