Rapid detection of KPC-producing Enterobacterales by using a modified Carba NP test with imipenem/relebactam

Introduction: Here, we propose a novel modified Carba NP test for detecting KPC-producing Enterobacterales using imipenem/relebactam.

Material and methods: The test performance was evaluated in a random selection of 160 previously molecularly characterized clinical isolates carrying the 110 bla_KPC, 1 bla_GES, 12 bla_VIM, 4 bla_IMP, 3 bla_NDM and 42 bla_OXA-48-like genes. The proposed method relies on the detection of imipenem hydrolysis in an imipenem/relebactam antibiotic solution and subsequent visual interpretation by color change.

Results: All class A producing Enterobacterales (111/111) were detected using imipenem/relebactam as no visual appreciation of color change was perceived due to a nule hydrolysis of imipenem in the antibiotic solution. Overall, the assay showed 100% sensitivity (111/111) and specificity (69/69) for detecting class A KPC-producing Enterobacterales.

Discussion: The biochemical assay provides very reliable results for detecting KPC-producing Enterobacterales, with a turnaround time of less than 1 hour, minimum handling and no specialized equipment required.