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

Abstract

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 ISAba1 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 ISAba1-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.