Abstract
<jats:p> Objective: Carbapenem-resistant <jats:italic>Klebsiella pneumoniae</jats:italic> harboring <jats:italic>bla</jats:italic> <jats:sub>NDM</jats:sub> poses a serious threat to public health; however, <jats:italic>bla</jats:italic> <jats:sub>NDM-15</jats:sub> remains poorly characterized outside the dominant epidemic lineages. Methods: We characterized <jats:italic>K. pneumoniae</jats:italic> strain ETFK6090, isolated from a perianal surveillance swab of an 11-month-old immunocompromised child in a paediatric intensive care unit. Investigations included antimicrobial susceptibility testing, broth conjugation, S1 nuclease PFGE with Southern blotting, complete genome sequencing, and comparative genomic analysis against 465 curated <jats:italic>bla</jats:italic> <jats:sub>NDM</jats:sub> -positive <jats:italic>K. pneumoniae</jats:italic> genomes from 37 countries. Results: ETFK6090 belonged to ST580 and exhibited resistance to carbapenems, ceftazidime-avibactam, broad-spectrum cephalosporins, fluoroquinolones, gentamicin, chloramphenicol and trimethoprim-sulfamethoxazole; amikacin and fosfomycin retained low MICs. The complete genome comprised one chromosome and five plasmids, <jats:italic>bla</jats:italic> <jats:sub>NDM-15</jats:sub> was localized on a 46,161-bp IncX3 plasmid, confirmed by Southern blotting. Conjugation into <jats:italic>Escherichia coli</jats:italic> EC600 transferred carbapenem and cephalosporin resistance, confirming in vitro mobility. The <jats:italic>bla</jats:italic> <jats:sub>NDM-15</jats:sub> genetic environment retained a conserved <jats:italic>bla</jats:italic> <jats:sub>NDM</jats:sub> module, with IS-mediated rearrangements at the downstream boundary. In the global comparison, <jats:italic>bla</jats:italic> <jats:sub>NDM-1</jats:sub> and <jats:italic>bla</jats:italic> <jats:sub>NDM-5</jats:sub> predominated, the ST580- <jats:italic>bla</jats:italic> <jats:sub>NDM-15</jats:sub> combination was exceedingly rare, and ETFK6090 constituted a distinct branch apart from major epidemic lineages. Conclusions: A transferable IncX3- <jats:italic>bla</jats:italic> <jats:sub>NDM-15</jats:sub> plasmid can emerge in an uncommon ST580 background, underscoring the necessity to extend genomic surveillance of carbapenem-resistant <jats:italic>K. pneumoniae</jats:italic> beyond dominant epidemic clones, particularly in high-risk paediatric and intensive-care settings. </jats:p>