Functional export of NDM-7 to outer membrane vesicles in Klebsiella pneumoniae compromises imipenem and cefiderocol activity

The carbapenemases Klebsiella pneumoniae carbapenemase (KPC) and New Delhi metallo-β-lactamase (NDM) are the most widespread determinants of carbapenem resistance in Klebsiella pneumoniae . Whereas KPC is a soluble periplasmic serine-β-lactamase, NDM is a membrane-anchored metallo-β-lactamase (MBL), a feature that promotes its incorporation into outer membrane vesicles (OMVs). OMVs are naturally released nanoparticles that deliver diverse bioactive cargo, including enzymes, virulence factors, and signaling molecules, and may contribute to antibiotic resistance. Here, we investigated the export and activity of carbapenemases in OMVs produced by carbapenem-resistant Klebsiella pneumoniae clinical isolates expressing NDM-7, an emerging NDM variant, or KPC-2, as well as in isogenic laboratory-derived K. pneumoniae strains producing NDM-1, NDM-7, or KPC-2. NDM enzymes were detected in vesicles released by NDM-producing strains, whereas KPC-2 was detected in whole-cell lysates but not observed in purified OMVs. OMVs contained catalytically active NDM enzyme and conferred protection to susceptible K. pneumoniae against imipenem. Importantly, NDM-positive OMVs also promoted the survival of susceptible bacteria during exposure to cefiderocol, a siderophore cephalosporin used to treat infections caused by MBL producers, allowing the recipient strain to grow at otherwise inhibitory concentrations. This protective effect was more pronounced for NDM-7 than for NDM-1. Together, these findings show that the clinically emerging NDM-7 variant is efficiently packaged into OMVs in K. pneumoniae and remains enzymatically active, allowing extracellular antibiotic degradation and conferring protection to susceptible bacteria exposed to carbapenems and cefiderocol.