Rapid Identification of Klebsiella pneumoniae by Matrix-Assisted Laser Desorption/Ionization-Time of Flight Mass Spectrometry and Detection of Meropenem Resistance by Flow Cytometric Assay.

Background The aim of this study was to develop a rapid detection method of carbapenem-resistant Klebsiella pneumoniae (CRKP) strains both MALDI-TOF MS and flow cytometry (FCM). Methods A total of 174 K. pneumoniae strains were included in this study. Molecular characterization of carbapenemase gene was performed by PCR. Bacterial identification was performed by MALDI-TOF-MS. Meropenem susceptibility was tested at the concentrations of breakpoints described by the Clinical and Laboratory Standards Institute (CLSI) guide by FCM. Results Sixty-two CRKP were positive for at least one carbapenemase gene. A total of 174 K. pneumoniae isolates obtained from clinically relevant material were correctly identified by Bruker MALDI-TOF MS with log (score) >2.0. These results were 100% concordant with the Phoenix™ Automated Microbiology System (BD, MD) and conventional identification results. Based on the analysis of the receiver operating characteristic (ROC) curves, the best validity and sensitivity data were obtained with a cut-off value of 18.88% by FCM. The concordance, sensitivity, and specificity for FCM by the selected cut-off values were 99.4%, 98.9%, and 100%, respectively. Conclusions We conclude that reliable results on bacterial identification and meropenem susceptibility test can be obtained within 2 hr combined by MALDI-TOF-MS and FCM.