MALDI biotyper - Phenotypic identification test rapid assay (MBT-PITRA): A new method to detect KPC and NDM in Enterobacterales.

Carbapenemase-producing Enterobacterales are a growing concern in public health. In order to rapidly determine the antimicrobial profile, the MALDI Biotyper - antibiotic susceptibility test rapid assay (MBT-ASTRA) was developed, based on the relative growth of bacteria in the presence of antibiotics. In this study, we added carbapenemase enzymatic inhibitors to the MBT-ASTRA and developed an adapted method named MALDI Biotyper - Phenotypic Identification Test Rapid Assay (MBT-PITRA) in order to perform a rapid and cost-effective phenotypic test to detect Klebsiella pneumoniae carbapenemase (KPC) and New Delhi metallo-beta-lactamase (NDM), including co-producers, in Enterobacterales. Fifty-nine clinical isolates of carbapenemase-producing Enterobacterales and 28 non-carbapenemase-producing isolates collected from 2013 to 2023 were assessed using this approach. The MBT-PITRA method involved incubating bacterial isolates with different solutions of meropenem plus enzymatic inhibitors, phenylboronic acid and/or ethylenediaminetetraacetic acid, followed by analysis using MALDI-TOF MS. Carbapenemase production was inferred based on relative growth (RG) values calculated from peak intensities in the presence and absence of enzymatic inhibitors. KPC-producing isolates presented 90 % (18/20) concordance, while isolates positive for NDM (16/16), KPC plus NDM (14/14) and negative (28/28) for carbapenemases were 100 % correctly identified. MBT-PITRA demonstrated to be a promising method for identification of carbapenemases. IMPORTANCE: The MBT-PITRA appears to be a promising method for the rapid detection of carbapenemases in Enterobacterales.