{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,14]],"date-time":"2026-09-14T06:04:26Z","timestamp":1789365866946,"version":"build-2803163510"},"reference-count":20,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,9,14]],"date-time":"2026-09-14T00:00:00Z","timestamp":1789344000000},"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. Microbiol."],"abstract":"\n Purpose<\/jats:title>\n To investigate the molecular epidemiology and resistance mechanisms of carbapenem-resistant Enterobacteriaceae (CRE) with a specific phenotype resistant to ertapenem, but susceptible to meropenem and imipenem.<\/jats:p>\n <\/jats:sec>\n \n Methods<\/jats:title>\n \n Escherichia coli<\/jats:italic>\n isolates (\n n<\/jats:italic>\n \u202f=\u202f424) were collected across the country; 54 isolates were CRE, of which 14 isolates were resistant to ertapenem but susceptible to meropenem and imipenem. Antimicrobial susceptibility testing were conducted using 17 drugs on the 14 isolates. Whole-genome sequencing (WGS) was used to analyze the isolates\u2019 drug resistance genes carried, plasmid types, virulence genes, and drug resistance homology. Furthermore, efflux pumps and outer membrane proteins were analyzed.\n <\/jats:p>\n <\/jats:sec>\n \n Results<\/jats:title>\n \n Only 25.9% of the CRE isolates were resistant to ertapenem, and no carbapenemase genes were detected in any isolate. All 14 isolates carried the genes encoding extended-spectrum \u03b2-lactamase (ESBLs), and 8\n bla<\/jats:italic>\n CTX-M<\/jats:sub>\n subtypes were identified. Among these,\n bla<\/jats:italic>\n CTX-M-15<\/jats:sub>\n (5 isolates) and\n bla<\/jats:italic>\n CTX-M-14<\/jats:sub>\n (3 isolates) were the most prevalent. IncF plasmids (IncFIB, IncFIA, and IncFII) were the predominant plasmid types. Ten isolates simultaneously carried the highly virulent genes\n iucC<\/jats:italic>\n and\n iutA<\/jats:italic>\n . Efflux pump inhibition experiments with 14 isolates yielded negative results. Outer membrane protein analysis revealed that five of the isolates lacked OmpC. After genetic complementation with the outer membrane protein\n ompC<\/jats:italic>\n gene, the minimum inhibitory concentration of ertapenem decreased 16\u2013533 fold. Nine isolates with detectable OmpC expression also presented ertapenem monoresistance. Porin-coding gene disruption,\n ramA\/marA<\/jats:italic>\n gain-of-function mutations and efflux overexpression were excluded. Although these isolates harbored ESBL-encoding genes, ESBL alone could not confer ertapenem resistance. Potential mechanisms may include post-transcriptional porin repression, chromosomal\n ompC<\/jats:italic>\n up-regulation or other permeability-altering chromosomal variants, and their precise mechanisms remain to be elucidated.\n <\/jats:p>\n <\/jats:sec>\n \n Conclusion<\/jats:title>\n \n These results suggest that the loss of outer membrane protein OmpC may be a key factor contributing to ertapenem resistance in carbapenemase-negative\n E. coli<\/jats:italic>\n strains, and efflux pumps do not appear to mediate this resistance phenotype.\n <\/jats:p>\n <\/jats:sec>","DOI":"10.3389\/fmicb.2026.1937582","type":"journal-article","created":{"date-parts":[[2026,9,14]],"date-time":"2026-09-14T05:40:12Z","timestamp":1789364412000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Molecular epidemiology and mechanisms of Escherichia coli resistance to ertapenem but not other carbapenems in China"],"prefix":"10.3389","volume":"17","author":[{"given":"Dongliang","family":"Wang","sequence":"first","affiliation":[{"name":"Department of Critical Care Medicine, Gansu Provincial Hospital","place":["Lanzhou, Gansu Province, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yuan","family":"Yuan","sequence":"additional","affiliation":[{"name":"Department of Critical Care Medicine, Longhua Hospital Affiliated to Shanghai University of Traditional Chinese Medicine","place":["Shanghai, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Wenjing","family":"Li","sequence":"additional","affiliation":[{"name":"Gansu University of Chinese Medicine","place":["Lanzhou, Gansu, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Junshuai","family":"Feng","sequence":"additional","affiliation":[{"name":"Department of Critical Care Medicine, Gansu Provincial Hospital","place":["Lanzhou, Gansu Province, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Tianpeng","family":"He","sequence":"additional","affiliation":[{"name":"Department of Critical Care Medicine, Gansu Provincial Hospital","place":["Lanzhou, Gansu Province, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2026,9,14]]},"reference":[{"key":"ref1","doi-asserted-by":"publisher","first-page":"ofab643","DOI":"10.1093\/ofid\/ofab643","article-title":"Distinctive features of ertapenem-mono-resistant carbapenem-resistant enterobacterales in the United States: a cohort study","volume":"9","author":"Adelman","year":"2021","journal-title":"Open Forum Infect. 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Agents"},{"key":"ref18","doi-asserted-by":"publisher","first-page":"1690","DOI":"10.3390\/microorganisms11071690","article-title":"Outer membrane porins contribute to antimicrobial resistance in gram-negative bacteria","volume":"11","author":"Zhou","year":"2023","journal-title":"Microorganisms"}],"container-title":["Frontiers in Microbiology"],"original-title":[],"link":[{"URL":"https:\/\/www.frontiersin.org\/articles\/10.3389\/fmicb.2026.1937582\/full","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,9,14]],"date-time":"2026-09-14T05:40:13Z","timestamp":1789364413000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.frontiersin.org\/articles\/10.3389\/fmicb.2026.1937582\/full"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,9,14]]},"references-count":20,"alternative-id":["10.3389\/fmicb.2026.1937582"],"URL":"https:\/\/doi.org\/10.3389\/fmicb.2026.1937582","relation":{},"ISSN":["1664-302X"],"issn-type":[{"value":"1664-302X","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,9,14]]},"article-number":"1937582"}}