Evaluation of rapid KPC carbapenemase detection method based on MALDI-TOF VITEK MS spectra analysis

Clinical microbiology laboratories in hospital settings need to be able to identify patients who carry carbapenemase-producing bacterial strains quickly in order to contain their spread and initiate proper pharmacological therapy. The aim of this study was to confirm the correlation between KPC production and a characteristic mass spectrometry (MS) peak (11 109 Da +/- 8) to validate the use of matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) MS as a rapid screening tool. With this aim, 176 selected clinical samples that were KPC-producing and 260 control samples that were carbapenem-susceptible or carbapenem-resistant through other resistance mechanisms, or were producing hydrolytic enzymes other than KPC, were analysed. The presence of the 11 109 Da peak in the spectra of 99.4% (175/176) of the KPC-producing strains compared to the controls, which all lacked the peak, confirmed a strong correlation between KPC production and the presence of the 11 109 Da peak in the MALDI-TOF MS spectrum. The high sensitivity (98.7 %) and specificity (100 %) of the peak searching in the MALDI-TOF MS spectra mean that 11 109 Da peak searching is a suitable screening tool in KPC-endemic regions.