Direct detection of intact Klebsiella pneumoniae carbapenemase variants from cell lysates: Identification, characterization and clinical implications

•LC-MS methods are used to identify intact Klebsiella pneumoniae carbapenemase (KPC).•Mass spectrometry validates the mature form of KPC based on molecular weight.•Combining top-down and bottom-up proteomics confirms mature protein sequence of KPC.•This method can be applied to multiple variants, including KPC-2 through KPC-5.•The method can be easily adapted for KPC determination from any bacterial pathogen.