{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,27]],"date-time":"2026-08-27T05:17:45Z","timestamp":1787807865822,"version":"build-2784847793"},"reference-count":41,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,8,27]],"date-time":"2026-08-27T00:00:00Z","timestamp":1787788800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Cell. Infect. Microbiol."],"abstract":"<jats:sec>\n                    <jats:title>Objectives<\/jats:title>\n                    <jats:p>\n                      To assess cefiderocol activity against carbapenem-resistant\n                      <jats:italic>Klebsiella pneumoniae<\/jats:italic>\n                      (CRKP) bloodstream isolates collected before local clinical introduction and to characterize the distribution of borderline MIC elevation across major genomic backgrounds.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>\n                      We retrospectively analyzed 389 episodes of\n                      <jats:italic>K. pneumoniae<\/jats:italic>\n                      bloodstream infection at a tertiary hospital in China during 2018-2024. All 83 carbapenem-resistant isolates underwent cefiderocol broth microdilution testing and whole-genome sequencing. For epidemiological analysis, reduced susceptibility was prespecified as an MIC of 4\u201316 mg\/L and was not intended to replace clinical breakpoint interpretation.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>\n                      CRKP accounted for 21.3% of\n                      <jats:italic>K. pneumoniae<\/jats:italic>\n                      bloodstream infections and remained associated with in-hospital mortality after adjustment for infection severity and source. By CLSI criteria, 83.1% of isolates were cefiderocol susceptible; the MIC\n                      <jats:sub>50<\/jats:sub>\n                      and MIC\n                      <jats:sub>90<\/jats:sub>\n                      were 4 and 8 mg\/L, respectively, and 41.0% met the reduced-susceptibility definition. ST11 predominated, with KL47 and KL64 as the main capsular loci. Cefiderocol MICs were higher among KL47\/KL64 and virulence-plasmid-associated isolates than among comparator backgrounds. In multivariable analysis,\n                      <jats:italic>bla<\/jats:italic>\n                      <jats:sub>NDM-1<\/jats:sub>\n                      ,\n                      <jats:italic>bla<\/jats:italic>\n                      <jats:sub>SHV-12<\/jats:sub>\n                      , and the aerobactin locus remained associated with reduced susceptibility, although the findings require cautious interpretation because of limited sample size and possible effects of clonal background. No inactivating mutations were identified in\n                      <jats:italic>cirA<\/jats:italic>\n                      ,\n                      <jats:italic>fepA<\/jats:italic>\n                      , or\n                      <jats:italic>fiu<\/jats:italic>\n                      .\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>Borderline cefiderocol MIC elevation was present before local drug exposure and was more frequent in locally prevalent ST11-KL47\/KL64 and virulence-plasmid-associated CRKP. These findings provide a bloodstream-specific pre-introduction baseline and support prospective surveillance of numerical MIC distributions and associated genomic backgrounds.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.3389\/fcimb.2026.1890499","type":"journal-article","created":{"date-parts":[[2026,8,27]],"date-time":"2026-08-27T04:26:06Z","timestamp":1787804766000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Genetic characterization of carbapenem-resistant Klebsiella pneumoniae bloodstream isolates with reduced susceptibility to cefiderocol"],"prefix":"10.3389","volume":"16","author":[{"given":"Min","family":"Wang","sequence":"first","affiliation":[{"name":"Department of Laboratory Medicine, The Affiliated Taian City Central Hospital of Qingdao University","place":["Taian, China"]},{"name":"Shandong Provincial Key Medical and Health Laboratory of Anti-Drug Resistant Drug Research, The Affiliated Taian City Central Hospital of Qingdao University","place":["Taian, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Xue","family":"Wu","sequence":"additional","affiliation":[{"name":"Department of Pain Management, The Affiliated Taian City Central Hospital of Qingdao University","place":["Taian, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ning","family":"Yuan","sequence":"additional","affiliation":[{"name":"Binhai New Area Hospital of Traditional Chinese Medicine (TCM)","place":["Tianjin, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Lin","family":"Li","sequence":"additional","affiliation":[{"name":"Pharmacy Intravenous Admixture Services, The Affiliated Taian City Central Hospital of Qingdao University","place":["Taian, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Zhijun","family":"Zhang","sequence":"additional","affiliation":[{"name":"Department of Laboratory Medicine, The Affiliated Taian City Central Hospital of Qingdao University","place":["Taian, China"]},{"name":"Shandong Provincial Key Medical and Health Laboratory of Anti-Drug Resistant Drug Research, The Affiliated Taian City Central Hospital of Qingdao University","place":["Taian, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2026,8,27]]},"reference":[{"key":"B1","doi-asserted-by":"publisher","first-page":"455","DOI":"10.1089\/cmb.2012.0021","article-title":"SPAdes: a new genome assembly algorithm and its applications to single-cell sequencing","volume":"19","author":"Bankevich","year":"2012","journal-title":"J. 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