{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,1]],"date-time":"2026-09-01T01:15:21Z","timestamp":1788225321698,"version":"build-2803163510"},"reference-count":39,"publisher":"American Society for Microbiology","issue":"2","license":[{"start":{"date-parts":[[2026,2,3]],"date-time":"2026-02-03T00:00:00Z","timestamp":1770076800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"},{"start":{"date-parts":[[2026,2,3]],"date-time":"2026-02-03T00:00:00Z","timestamp":1770076800000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/journals.asm.org\/non-commercial-tdm-license"}],"content-domain":{"domain":["journals.asm.org"],"crossmark-restriction":true},"short-container-title":["Microbiol Spectr"],"published-print":{"date-parts":[[2026,2,3]]},"abstract":"<jats:title>ABSTRACT<\/jats:title>\n                  <jats:sec>\n                    <jats:title\/>\n                    <jats:p>\n                      <jats:italic toggle=\"yes\">Klebsiella quasipneumoniae<\/jats:italic>\n                      is an emerging opportunistic pathogen increasingly associated with multidrug-resistant infections. In this study, we characterized four clinical isolates of\n                      <jats:italic toggle=\"yes\">K. quasipneumoniae<\/jats:italic>\n                      subsp.\n                      <jats:italic toggle=\"yes\">quasipneumoniae<\/jats:italic>\n                      assigned to the ST978-KL103 clonotype, all linked to poor clinical outcomes. Antimicrobial susceptibility testing revealed an extensively drug-resistant phenotype, including resistance to \u03b2-lactams, carbapenems, aminoglycosides, fluoroquinolones, tigecycline, and trimethoprim\/sulfamethoxazole, with polymyxin B as the only effective agent. Whole-genome sequencing and comparative analysis showed that all ST978-KL103 isolates harbored multiple plasmids, including a conserved IncU-type plasmid carrying\n                      <jats:italic toggle=\"yes\">bla<\/jats:italic>\n                      <jats:sub>IMP-4<\/jats:sub>\n                      and the\n                      <jats:italic toggle=\"yes\">tmexCD2-toprJ2<\/jats:italic>\n                      tigecycline resistance cluster. Two isolates also carried IncC-type plasmids encoding\n                      <jats:italic toggle=\"yes\">bla<\/jats:italic>\n                      <jats:sub>NDM-1<\/jats:sub>\n                      . Conjugation assays confirmed efficient horizontal transfer of both plasmid types to\n                      <jats:italic toggle=\"yes\">E. coli<\/jats:italic>\n                      recipients. Although classical virulence loci such as yersiniabactin, aerobactin, and\n                      <jats:italic toggle=\"yes\">rmpA<\/jats:italic>\n                      \/\n                      <jats:italic toggle=\"yes\">rmpA2<\/jats:italic>\n                      were absent, the isolates exhibited strong biofilm formation and serum resistance, indicating potential for persistence and immune evasion. Cytotoxicity assays and\n                      <jats:italic toggle=\"yes\">Galleria mellonella<\/jats:italic>\n                      infection models demonstrated low acute virulence compared to the hypervirulent\n                      <jats:italic toggle=\"yes\">K. pneumoniae<\/jats:italic>\n                      strain NUTH-K2044. Phylogenetic analysis placed the ST978 isolates within a distinct and globally distributed clonal lineage. The close genetic relatedness among isolates, particularly between KP57 and KP58, suggests recent nosocomial transmission. Resistome profiling of nine global ST978 genomes revealed over 40 resistance genes, with our isolates uniquely harboring the\n                      <jats:italic toggle=\"yes\">tmexCD2-toprJ2<\/jats:italic>\n                      cluster. These findings highlight ST978\n                      <jats:italic toggle=\"yes\">K. quasipneumoniae<\/jats:italic>\n                      as a globally disseminated and increasingly drug-resistant lineage with the potential to emerge as a high-risk clone in clinical settings.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>IMPORTANCE<\/jats:title>\n                    <jats:p>\n                      The emergence of extensively drug-resistant\n                      <jats:italic toggle=\"yes\">Klebsiella quasipneumoniae<\/jats:italic>\n                      strains poses a significant threat to global health yet remains underrecognized due to diagnostic limitations. Our study identifies ST978-KL103 as a cryptic high-risk lineage co-harboring\n                      <jats:italic toggle=\"yes\">bla<\/jats:italic>\n                      <jats:sub>IMP-4<\/jats:sub>\n                      ,\n                      <jats:italic toggle=\"yes\">bla<\/jats:italic>\n                      <jats:sub>NDM-1<\/jats:sub>\n                      , and tmexCD2-toprJ2 on transferable plasmids. These findings highlight the species\u2019 underappreciated role as a reservoir and disseminator of last-line resistance. The strong biofilm formation and serum resistance further suggest persistence potential in clinical settings. Early recognition and surveillance of such emerging clones are critical to prevent silent dissemination and therapeutic failure in healthcare environments.\n                    <\/jats:p>\n                  <\/jats:sec>","DOI":"10.1128\/spectrum.02622-25","type":"journal-article","created":{"date-parts":[[2025,12,19]],"date-time":"2025-12-19T14:01:00Z","timestamp":1766152860000},"update-policy":"https:\/\/doi.org\/10.1128\/asmj-crossmark-policy-page","source":"Crossref","is-referenced-by-count":0,"title":["Characterization of multidrug-resistant ST978-KL103\n                    <i>Klebsiella quasipneumoniae<\/i>\n                    subsp.\n                    <i>quasipneumoniae<\/i>\n                    clinical strains co-harboring\n                    <i>tmexCD2-toprJ2<\/i>\n                    and\n                    <i>bla<\/i>\n                    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