Rapid Identification of Carbapenemase-producing Klebsiella pneumoniae strains by Matrix-Assisted Laser Desorption/Ionization-Time of Flight using Vitek® Mass Spectrometry System

Objective: The analysis of the protein pattern of Klebsiella pneumoniae carbapenemase (KPC)-producing strains by Bruker Matrix-Assisted Laser Desorption Ionization (MALDI) Biotyper system has revealed the presence, in the majority of cases, of an 11.109 m/z peak. The peak corresponds to the gene product named p019 of the blaKPC-bearing plasmids and has been suggested as a candidate for a biomarker that is able to distinguish KPC-producers from non-KPC-producers. The aim of this study was to evaluate the rapid detection of the 11.109 m/z peak of KPC-producer strains in the clinical laboratory routine by Matrix-Assisted Laser Desorption Ionization-Time of Flight (MALDI-TOF) technique, using the Vitek® Research-User-Only (RUO) Mass Spectrometry (MS) system without changing the instrument parameters. Materials and Methods: Globally, 373 K. pneumoniae isolates were investigated and identified by MALDI-TOF MS analysis. KPC-producers were distinguished from non-KPC-producers by Antimicrobial Susceptibility Testing (AST) and phenotypic carbapenemase resistance assays. Results: The MALDI-TOF Vitek MS RUO detected the 11.109 m/z peak in 95.7% of KPC-producers with 100% specificity before traditional test results became available. Conclusion: Our approach is appropriate as a first screening step for the rapid identification of KPC isolates, which will help to improve infection control in clinical practice and prevent the outbreak and dissemination of resistant bacteria.