{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,2]],"date-time":"2026-10-02T04:55:58Z","timestamp":1790916958207,"version":"4.1.0"},"reference-count":15,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,10,2]],"date-time":"2026-10-02T00:00:00Z","timestamp":1790899200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100031514","name":"Health Commission of Chengdu Municipality","doi-asserted-by":"publisher","award":["2024248"],"award-info":[{"award-number":["2024248"]}],"id":[{"id":"10.13039\/100031514","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Immunol."],"abstract":"<jats:sec>\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>\n                      Apparent transitions in carbapenem susceptibility among sequential\n                      <jats:italic>Klebsiella pneumoniae<\/jats:italic>\n                      isolates are often interpreted as strain replacement. However, phenotypic variation among closely related isolates may also produce similar phenotypic shifts, particularly in heavily treated patients.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Case presentation<\/jats:title>\n                    <jats:p>\n                      We report a 91-year-old long-term hospitalized patient from whom three sequential ST11\n                      <jats:italic>Klebsiella pneumoniae<\/jats:italic>\n                      isolates were recovered from blood and urine over a 3-month period. The initial bloodstream isolate (KPB1) exhibited a hypermucoviscous phenotype, KPC production, and carbapenem resistance. A subsequent urinary isolate (KPU2) lost the hypermucoviscous phenotype and showed attenuation of carbapenem resistance, becoming susceptible to imipenem, meropenem, and doripenem while remaining resistant to ertapenem. A later urinary isolate (KPU3) reverted to carbapenem resistance while remaining non-hypermucoviscous. Repeat antimicrobial testing confirmed these findings. Core-genome SNP analysis identified 16\u201320 pairwise differences among the three isolates, supporting close genomic relatedness despite their phenotypic discordance.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusion<\/jats:title>\n                    <jats:p>\n                      This case illustrates marked differences in carbapenem susceptibility and hypermucoviscosity among closely related ST11\n                      <jats:italic>K. pneumoniae<\/jats:italic>\n                      isolates recovered during a single patient\u2019s clinical course. KPU2 retained ertapenem resistance despite susceptibility to other tested carbapenems. The genomic findings were more consistent with closely related isolates than with replacement by an unrelated strain, although direct ancestry and continuous persistence could not be established. Phenotypic changes should be interpreted alongside repeat microbiological testing, available genomic evidence, and the clinical context.\n                    <\/jats:p>\n                  <\/jats:sec>","DOI":"10.3389\/fimmu.2026.1857429","type":"journal-article","created":{"date-parts":[[2026,10,2]],"date-time":"2026-10-02T04:41:41Z","timestamp":1790916101000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Closely related ST11 Klebsiella pneumoniae isolates with transient attenuation and re-emergence of carbapenem resistance during prolonged hospitalization: a case report"],"prefix":"10.3389","volume":"17","author":[{"given":"Mingquan","family":"Zeng","sequence":"first","affiliation":[{"name":"Department of Intensive Care Medicine, The Fourth People\u2019s Hospital of Chengdu","place":["Chengdu, China"]},{"name":"Department of Intensive Care Medicine, The Clinical Hospital of Chengdu Brain Science Institute, MOE Key Lab for Neuroinformation, University of Electronic Science and Technology of China","place":["Chengdu, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yu","family":"Jiang","sequence":"additional","affiliation":[{"name":"Department of Clinical Laboratory, The Fourth People\u2019s Hospital of Chengdu","place":["Chengdu, China"]},{"name":"Department of Clinical Laboratory, The Clinical Hospital of Chengdu Brain Science Institute, MOE Key Lab for Neuroinformation, University of Electronic Science and Technology of China","place":["Chengdu, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Fei","family":"Yan","sequence":"additional","affiliation":[{"name":"Department of Clinical Laboratory, The Fourth People\u2019s Hospital of Chengdu","place":["Chengdu, China"]},{"name":"Department of Clinical Laboratory, The Clinical Hospital of Chengdu Brain Science Institute, MOE Key Lab for Neuroinformation, University of Electronic Science and Technology of China","place":["Chengdu, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yuting","family":"Sun","sequence":"additional","affiliation":[{"name":"Department of Clinical Laboratory, The Fourth People\u2019s Hospital of Chengdu","place":["Chengdu, China"]},{"name":"Department of Clinical Laboratory, The Clinical Hospital of Chengdu Brain Science Institute, MOE Key Lab for Neuroinformation, University of Electronic Science and Technology of China","place":["Chengdu, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Heng","family":"Liao","sequence":"additional","affiliation":[{"name":"Department of Pharmacy, The Fourth People\u2019s Hospital of Chengdu","place":["Chengdu, China"]},{"name":"Department of Pharmacy, The Clinical Hospital of Chengdu Brain Science Institute, MOE Key Lab for Neuroinformation, University of Electronic Science and Technology of China","place":["Chengdu, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Weiguo","family":"Zhou","sequence":"additional","affiliation":[{"name":"Department of Intensive Care Medicine, The Fourth People\u2019s Hospital of Chengdu","place":["Chengdu, China"]},{"name":"Department of Intensive Care Medicine, The Clinical Hospital of Chengdu Brain Science Institute, MOE Key Lab for Neuroinformation, University of Electronic Science and Technology of China","place":["Chengdu, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2026,10,2]]},"reference":[{"key":"B1","doi-asserted-by":"publisher","DOI":"10.1128\/mbio.02906-22","article-title":"Within-host genotypic and phenotypic diversity of contemporaneous carbapenem-resistant Klebsiella pneumoniae from blood cultures of patients with 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