Evaluation of the Novodiag CarbaR+, a Novel Integrated Sample to Result Platform for the Multiplex Qualitative Detection of Carbapenem and Colistin Resistance Markers

Objectives: This study evaluated the performance of the Novodiag ® CarbaR+ an automated qualitative nucleic acid-based diagnostic assay detecting the bla VIM , bla NDM , bla IMP , bla OXA-48 , bla KPC , bla OXA-23 , bla OXA-58 , bla OXA-24 , and IS Aba 1 associated bla OXA-51 carbapenemase genes and colistin resistance mcr-1 gene from clinical isolates or directly from rectal swabs. Materials and Methods: CarbaR+ was evaluated on 201 clinical isolates and on 100 rectal swabs (80 selected swabs from patients that were evaluated by culture method and/or Xpert Carba-R assay and 20 spiked samples). PCR-sequencing on colonies was considered as the gold standard. Results: The CarbaR+ detected all the variants of the targeted resistance genes (39 bla VIM- , 30 bla NDM- , 20 bla IMP- , 19 bla OXA-48- , 15 bla KPC- , 19 bla OXA-23- , 13 bla OXA-58- , 4 bla OXA-24- , 8 IS Aba 1- bla OXA-51- , and 3 mcr-1 -like genes) with sensitivity and specificity of 98.2% and 99.7%, respectively. On the 80 rectal swabs, 71 CarbaR+ results were fully concordant with the results on selective culture media (66 positive samples with 1 to 3 carbapenemases and 5 negative samples). In eight rectal swabs, CarbaR+ identified additional carbapenemase genes. One false negative result with an Escherichia coli producing-OXA-181 was observed and one CarbaR+ result for OXA-48 was in agreement with Xpert Carba-R assay, without growth on culture media. A concordance of 100% was observed on spiked samples. Conclusions: Novodiag CarbaR+ is a random-access fully automated system that achieves excellent performances for the detection of carbapenemase and/or colistin resistance determinants either from cultured clinical isolates or directly from rectal swabs in 80 minutes.