{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T09:27:09Z","timestamp":1785403629646,"version":"3.56.0"},"reference-count":28,"publisher":"American Society for Microbiology","issue":"4","license":[{"start":{"date-parts":[[2026,4,7]],"date-time":"2026-04-07T00:00:00Z","timestamp":1775520000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"},{"start":{"date-parts":[[2026,4,7]],"date-time":"2026-04-07T00:00:00Z","timestamp":1775520000000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/journals.asm.org\/non-commercial-tdm-license"}],"funder":[{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["82302574"],"award-info":[{"award-number":["82302574"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["82172311"],"award-info":[{"award-number":["82172311"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"name":"China Antimicrobial Surveillance Network","award":["2020QD049"],"award-info":[{"award-number":["2020QD049"]}]}],"content-domain":{"domain":["journals.asm.org"],"crossmark-restriction":true},"short-container-title":["Microbiol Spectr"],"published-print":{"date-parts":[[2026,4,7]]},"abstract":"<jats:title>ABSTRACT<\/jats:title>\n                  <jats:sec>\n                    <jats:title\/>\n                    <jats:p>\n                      KPC variants are the primary cause of treatment failure in patients with\n                      <jats:italic toggle=\"yes\">Klebsiella pneumoniae<\/jats:italic>\n                      infections. This study reports the molecular mechanism by which two novel KPC variants (KPC-194 and KPC-33), isolated from a single patient, mediate resistance to ceftazidime-avibactam in ST11-KL64\n                      <jats:italic toggle=\"yes\">K. pneumoniae<\/jats:italic>\n                      , as well as the evolutionary trajectory of these variants within the host. The broth microdilution method (BMD) was used to determine bacterial susceptibility to antimicrobial agents. Whole-genome sequencing (WGS) technology was employed to identify the drug-resistant genes, virulence genes, and genetic environment carried by the bacterial strains. Molecular cloning experiments and plasmid conjugation experiments were conducted to clarify the susceptibility of KPC-194 to ceftazidime-avibactam and carbapenem. The BMD showed that the KPC-194-producing\n                      <jats:italic toggle=\"yes\">K. pneumoniae<\/jats:italic>\n                      strain was resistant to ceftazidime-avibactam and other antimicrobial agents but susceptible to imipenem (with a minimum inhibitory concentration [MIC] of 0.5 mg\/L). Compared with KPC-2, KPC-194 had two amino acid changes, namely, D179Y and P183L. In comparison with\n                      <jats:italic toggle=\"yes\">Escherichia coli<\/jats:italic>\n                      EC 600, the MIC of ceftazidime-avibactam against\n                      <jats:italic toggle=\"yes\">E. coli<\/jats:italic>\n                      EC 600 carrying the\n                      <jats:italic toggle=\"yes\">bla<\/jats:italic>\n                      <jats:sub>KPC-194<\/jats:sub>\n                      plasmid increased by 256-fold. When compared with pHSG398-DH5\u03b1, the MIC of ceftazidime-avibactam against the cloned strain\n                      <jats:italic toggle=\"yes\">bla<\/jats:italic>\n                      <jats:sub>KPC-194<\/jats:sub>\n                      -pHSG398-DH5\u03b1 was elevated by 64-fold. WGS revealed that\n                      <jats:italic toggle=\"yes\">bla<\/jats:italic>\n                      <jats:sub>KPC-194<\/jats:sub>\n                      was located on both the IncFII(pHN7A8)-type plasmid and the IncR-type plasmid and that it was horizontally transferred from the IncR-type plasmid to the IncFII(pHN7A8)-type plasmid via an IS\n                      <jats:italic toggle=\"yes\">26<\/jats:italic>\n                      -mediated replicative transposition mechanism. This study elucidates the key mechanism by which the novel KPC variant, KPC-194 (D179Y\/P183L), mediates resistance to ceftazidime-avibactam.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>IMPORTANCE<\/jats:title>\n                    <jats:p>\n                      This study elucidates the critical molecular mechanism and evolutionary pathway of a novel KPC variant, KPC-194, that confers resistance to the last-resort antibiotic combination ceftazidime-avibactam in a high-risk\n                      <jats:italic toggle=\"yes\">Klebsiella pneumoniae<\/jats:italic>\n                      strain. We identified that two amino acid substitutions (D179Y\/P183L) in KPC-194 are responsible for ceftazidime-avibactam resistance. Crucially, our work reveals a dual-threat dynamic: the resistance phenotype is not only caused by the KPC mutation but also profoundly exacerbated by horizontal gene transfer.\n                      <jats:italic toggle=\"yes\">bla<\/jats:italic>\n                      <jats:sub>KPC-194<\/jats:sub>\n                      mobilized from a low-risk IncR plasmid to a highly transmissible IncFII plasmid via IS26-mediated replicative transposition. This event dramatically enhances the potential for widespread dissemination among clinical pathogens.\n                    <\/jats:p>\n                  <\/jats:sec>","DOI":"10.1128\/spectrum.03257-25","type":"journal-article","created":{"date-parts":[[2026,3,16]],"date-time":"2026-03-16T11:10:34Z","timestamp":1773659434000},"update-policy":"https:\/\/doi.org\/10.1128\/asmj-crossmark-policy-page","source":"Crossref","is-referenced-by-count":0,"title":["Within-host co-evolution of KPC variants: plasmid-mediated dissemination of\n                    <i>bla<\/i>\n                    <sub>Kpc-194<\/sub>\n                    and\n                    <i>bla<\/i>\n                    <sub>Kpc-33<\/sub>\n                    in ST11-KL64 hypervirulent\n                    <i>Klebsiella pneumoniae<\/i>\n                    driving ceftazidime-avibactam resistance"],"prefix":"10.1128","volume":"14","author":[{"ORCID":"https:\/\/orcid.org\/0009-0001-1436-3668","authenticated-orcid":false,"given":"Li","family":"Ding","sequence":"first","affiliation":[{"id":[{"id":"https:\/\/ror.org\/013q1eq08","id-type":"ROR","asserted-by":"publisher"}],"name":"Institute of Antibiotics, Huashan Hospital, Fudan University","place":["Shanghai, China"]},{"id":[{"id":"https:\/\/ror.org\/00w5h0n54","id-type":"ROR","asserted-by":"publisher"}],"name":"Key Laboratory of Clinical Pharmacology of Antibiotics, Ministry of Health","place":["Shanghai, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Xiangbing","family":"Wu","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/0234wv516","id-type":"ROR","asserted-by":"publisher"}],"name":"Department of Laboratory Medicine, Wenzhou Central Hospital","place":["Wenzhou, 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