Improved Blue Carba test and Carba NP test for detection and classification of major Class A and B carbapenemases, including dual producers, among Gram-negative bacilli.

Unlabelled: Prompt and precise identification of carbapenemase-producing organisms is crucial for guiding clinical antibiotic treatments and limiting transmission. Here, we propose modifying the Blue Carba test (BCT) and Carba NP-direct (CNPd) to identify molecular carbapenemase classes, including dual carbapenemase strains, by adding specific Class A and Class B inhibitors. We tested 171 carbapenemase-producing Gram-negative bacilli strains-21 in Class A (KPC, NMC, SME), 58 in Class B (IMP, VIM, NDM, SPM), and 92 with dual carbapenemase production (KPC+NDM, KPC+IMP, KPC+VIM), all previously positive with BCT or CNPd.