{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,13]],"date-time":"2026-08-13T08:28:17Z","timestamp":1786609697758,"version":"build-2736575974"},"reference-count":16,"publisher":"Oxford University Press (OUP)","issue":"9","license":[{"start":{"date-parts":[[2026,8,13]],"date-time":"2026-08-13T00:00:00Z","timestamp":1786579200000},"content-version":"vor","delay-in-days":9,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100005869","name":"University of Fribourg, Switzerland","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100005869","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100016143","name":"NARA","doi-asserted-by":"publisher","id":[{"id":"10.13039\/100016143","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100002329","name":"Federal Office of Public Health, Switzerland","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100002329","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2026,8,4]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:sec>\n                    <jats:title>Objectives<\/jats:title>\n                    <jats:p>We aimed to characterize the intrinsic AmpC \u03b2-lactamase (EMC-2) from an Escherichia marmotae clinical isolate recovered from a bloodstream infection, exhibiting resistance to broad-spectrum cephalosporins.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>Cloning experiments in Escherichia coli were performed to evaluate the impact of the respective AmpC enzymes on \u03b2-lactam susceptibility. Purification of the enzymes was performed by ion-exchange chromatography, and kinetic assays were performed by UV spectrophotometry.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>By comparing the sequence of this AmpC with that of a WT E. marmotae, four amino acid substitutions and one amino acid deletion at position 296 were identified. Furthermore, a promoter alteration was responsible for an enhanced gene expression. Production of EMC-2 in E. coli TOP10 conferred an extended-spectrum AmpC (ESAC) phenotype characterized by increased MICs of cefotaxime, cefepime and cefiderocol. Site-directed mutagenesis confirmed the important role of the Arg296 deletion in this phenotype.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>We showed that the intrinsic AmpC of E. marmotae can acquire both structural and regulatory modifications that broaden its substrate spectrum, leading to reduced susceptibility to clinically relevant \u03b2-lactams, including cefiderocol.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1093\/jac\/dkag271","type":"journal-article","created":{"date-parts":[[2026,7,24]],"date-time":"2026-07-24T11:39:27Z","timestamp":1784893167000},"source":"Crossref","is-referenced-by-count":0,"title":["Characterization of the intrinsic AmpC \u03b2-lactamase of\n                    <i>Escherichia marmotae<\/i>\n                    and its impact on decreased susceptibility to cefiderocol and resistance to broad-spectrum cephalosporins"],"prefix":"10.1093","volume":"81","author":[{"given":"Samanta","family":"Freire","sequence":"first","affiliation":[{"name":"Emerging Antibiotic Resistance, Medical and Molecular Microbiology, Faculty of Science and Medicine, University of Fribourg , Fribourg ,","place":["Switzerland"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sandra Martinez","family":"Alvarez","sequence":"additional","affiliation":[{"name":"Emerging Antibiotic Resistance, Medical and Molecular Microbiology, Faculty of Science and Medicine, University of Fribourg , Fribourg ,","place":["Switzerland"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7335-9001","authenticated-orcid":false,"given":"Jacqueline","family":"Findlay","sequence":"additional","affiliation":[{"name":"Emerging Antibiotic Resistance, Medical and Molecular Microbiology, Faculty of Science and Medicine, University of Fribourg , Fribourg ,","place":["Switzerland"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Miriam","family":"Vogel","sequence":"additional","affiliation":[{"name":"MCL, Medizinische Laboratorien , Niederwangen ,","place":["Switzerland"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1343-1622","authenticated-orcid":false,"given":"Patrice","family":"Nordmann","sequence":"additional","affiliation":[{"name":"Emerging Antibiotic Resistance, Medical and Molecular Microbiology, Faculty of Science and Medicine, University of Fribourg , Fribourg ,","place":["Switzerland"]},{"name":"Swiss National Reference Center for Emerging Antibiotic Resistance , Fribourg ,","place":["Switzerland"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5160-5286","authenticated-orcid":false,"given":"Laurent","family":"Poirel","sequence":"additional","affiliation":[{"name":"Emerging Antibiotic Resistance, Medical and Molecular Microbiology, Faculty of Science and Medicine, University of Fribourg , Fribourg ,","place":["Switzerland"]},{"name":"Swiss National Reference Center for Emerging Antibiotic Resistance , Fribourg ,","place":["Switzerland"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"286","published-online":{"date-parts":[[2026,8,13]]},"reference":[{"key":"2026081303403287900_dkag271-B1","doi-asserted-by":"publisher","first-page":"2130","DOI":"10.1099\/ijs.0.000228","article-title":"Escherichia marmotae sp. nov., isolated from faeces of Marmota himalayana","volume":"65","author":"Liu","year":"2015","journal-title":"Int J Syst Evol Microbiol"},{"key":"2026081303403287900_dkag271-B2","doi-asserted-by":"publisher","first-page":"e0203521","DOI":"10.1128\/spectrum.02035-21","article-title":"Escherichia marmotae\u2014a human pathogen easily misidentified as Escherichia coli","volume":"10","author":"Sivertsen","year":"2022","journal-title":"Microbiol 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