In vivo evolution to high-level cefiderocol resistance of NDM-1–producing Klebsiella pneumoniae, followed by intra-hospital cross-transmission

Cefiderocol, a new siderophore cephalosporin, is among the few agents active against carbapenem-resistant Enterobacterales (CRE)–producing metallo-β-lactamases [1]. Emergence of high-level resistance among CRE-producing metallo-β-lactamases has been reported after cefiderocol exposure, mediated by alterations of siderophore receptors involved in cefiderocol uptake [2–4]. However, similar mutants were shown to be affected by fitness defect that might impair their ability to disseminate in the absence of selective pressure [2].