{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,20]],"date-time":"2026-10-20T21:59:00Z","timestamp":1792533540821,"version":"4.5.0"},"reference-count":19,"publisher":"American Society for Microbiology","issue":"5","license":[{"start":{"date-parts":[[2026,5,6]],"date-time":"2026-05-06T00:00:00Z","timestamp":1778025600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"},{"start":{"date-parts":[[2026,5,6]],"date-time":"2026-05-06T00:00:00Z","timestamp":1778025600000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/journals.asm.org\/non-commercial-tdm-license"}],"funder":[{"name":"Brigham and Women's Hospital Department of Pathology","award":["Internal funds"],"award-info":[{"award-number":["Internal funds"]}]}],"content-domain":{"domain":["journals.asm.org"],"crossmark-restriction":true},"short-container-title":["Antimicrob Agents Chemother"],"published-print":{"date-parts":[[2026,5,6]]},"abstract":"<jats:title>ABSTRACT<\/jats:title>\n                  <jats:sec>\n                    <jats:title\/>\n                    <jats:p>\n                      Cefepime is generally recommended for treatment of clinically significant AmpC producers, including\n                      <jats:italic toggle=\"yes\">Citrobacter freundii<\/jats:italic>\n                      complex (\n                      <jats:italic toggle=\"yes\">Cfre<\/jats:italic>\n                      ),\n                      <jats:italic toggle=\"yes\">Enterobacter cloacae<\/jats:italic>\n                      complex (\n                      <jats:italic toggle=\"yes\">Eclo<\/jats:italic>\n                      ), and\n                      <jats:italic toggle=\"yes\">Klebsiella aerogenes<\/jats:italic>\n                      (\n                      <jats:italic toggle=\"yes\">Kaer<\/jats:italic>\n                      ). Clinicians increasingly use the results of multiplex PCR panels to make early treatment decisions, with cefepime often chosen when an AmpC producer is detected without a\n                      <jats:italic toggle=\"yes\">bla<\/jats:italic>\n                      <jats:sub>CTX-M<\/jats:sub>\n                      extended-spectrum beta-lactamase (ESBL) or carbapenemase. To understand the safety of this approach, we evaluated the prevalence of cefepime resistance among 4,687\n                      <jats:italic toggle=\"yes\">Cfre<\/jats:italic>\n                      ; 9,878\n                      <jats:italic toggle=\"yes\">Eclo<\/jats:italic>\n                      ; and 4,800\n                      <jats:italic toggle=\"yes\">Kaer<\/jats:italic>\n                      clinical isolates collected in our hospital network in New England, USA, from 2015 to 2024. We additionally reviewed Blood Culture Identification 2 (BCID2) (bioM\u00e9rieux) results for 136 blood cultures and the sequenced genomes of 184 isolates (14 cefepime-susceptible dose-dependent [SDD], 34 cefepime-resistant). Cefepime-SDD and cefepime-resistant isolates made up 0.4% (18\/4,687) and 1.3% (59\/4,687) of\n                      <jats:italic toggle=\"yes\">Cfre<\/jats:italic>\n                      , 2.0% (194\/9,879) and 3.0% (299\/9,879) of\n                      <jats:italic toggle=\"yes\">Eclo<\/jats:italic>\n                      , and 0.3% (16\/4,800) and 0.6% (28\/4,800) of\n                      <jats:italic toggle=\"yes\">Kaer<\/jats:italic>\n                      . Of 117\n                      <jats:italic toggle=\"yes\">Eclo<\/jats:italic>\n                      and\n                      <jats:italic toggle=\"yes\">Kaer<\/jats:italic>\n                      identified in blood cultures on the BCID2, 4.3% (5\/117) were cefepime-SDD or cefepime-resistant and negative for an ESBL or carbapenemase target. Among sequenced cefepime-SDD isolates, 21% (3\/14) carried an ESBL. Cefepime-resistant isolates carried diverse beta-lactamase genes, including ESBL genes, carbapenemase genes, and plasmid-borne\n                      <jats:italic toggle=\"yes\">ampC<\/jats:italic>\n                      . While reduced cefepime susceptibility was generally associated with carriage of more beta-lactamase genes, 57% of cefepime-SDD and 35% of cefepime-resistant isolates encoded only chromosomal\n                      <jats:italic toggle=\"yes\">ampC<\/jats:italic>\n                      . Our results highlight variable cefepime susceptibility rates for AmpC producers across clinical settings and demonstrate diverse mechanisms underlying reduced cefepime susceptibility.\n                    <\/jats:p>\n                  <\/jats:sec>","DOI":"10.1128\/aac.01661-25","type":"journal-article","created":{"date-parts":[[2026,3,27]],"date-time":"2026-03-27T13:00:19Z","timestamp":1774616419000},"update-policy":"https:\/\/doi.org\/10.1128\/asmj-crossmark-policy-page","source":"Crossref","is-referenced-by-count":1,"title":["Prevalence and genetics of cefepime resistance among the AmpC-producing organisms\n                    <i>Citrobacter freundii<\/i>\n                    complex,\n                    <i>Enterobacter cloacae<\/i>\n                    complex, and\n                    <i>Klebsiella aerogenes<\/i>"],"prefix":"10.1128","volume":"70","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-4141-531X","authenticated-orcid":true,"given":"Sarah M.","family":"Schrader","sequence":"first","affiliation":[{"id":[{"id":"https:\/\/ror.org\/04b6nzv94","id-type":"ROR","asserted-by":"publisher"}],"name":"Department of Pathology, Brigham and Women\u2019s Hospital","place":["Boston, USA"]},{"id":[{"id":"https:\/\/ror.org\/002pd6e78","id-type":"ROR","asserted-by":"publisher"}],"name":"Department of Pathology, Massachusetts General Hospital","place":["Boston, USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Zachary","family":"Pearson","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/04b6nzv94","id-type":"ROR","asserted-by":"publisher"}],"name":"Department of Pathology, Brigham and Women\u2019s Hospital","place":["Boston, USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Samantha","family":"Taffner","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/04py2rh25","id-type":"ROR","asserted-by":"publisher"}],"name":"Mass General Brigham","place":["Boston, USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1221-5725","authenticated-orcid":true,"given":"Sanjat","family":"Kanjilal","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/01zxdeg39","id-type":"ROR","asserted-by":"publisher"}],"name":"Department of Population Medicine, Harvard Medical School and Harvard Pilgrim Health Care Institute","place":["Boston, USA"]},{"id":[{"id":"https:\/\/ror.org\/00raa0r66","id-type":"ROR","asserted-by":"publisher"}],"name":"Division of Infectious Diseases, Department of Medicine, Brigham and Women's Hospital","place":["Boston, USA"]},{"id":[{"id":"https:\/\/ror.org\/04dkp9463","id-type":"ROR","asserted-by":"publisher"}],"name":"Department of Medical Microbiology and Infection Prevention, Amsterdam University Medical Center","place":["Amsterdam, the Netherlands"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5633-8746","authenticated-orcid":true,"given":"Nicole D.","family":"Pecora","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/04b6nzv94","id-type":"ROR","asserted-by":"publisher"}],"name":"Department of Pathology, Brigham and Women\u2019s Hospital","place":["Boston, USA"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"235","reference":[{"key":"e_1_3_4_2_2","doi-asserted-by":"publisher","DOI":"10.1093\/cid\/ciae403"},{"key":"e_1_3_4_3_2","doi-asserted-by":"publisher","DOI":"10.1093\/cid\/ciz173"},{"key":"e_1_3_4_4_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.cmi.2019.05.007"},{"key":"e_1_3_4_5_2","doi-asserted-by":"publisher","DOI":"10.1128\/AAC.01477-15"},{"key":"e_1_3_4_6_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.ijantimicag.2024.107115"},{"key":"e_1_3_4_7_2","doi-asserted-by":"publisher","DOI":"10.1093\/jacamr\/dlae087"},{"key":"e_1_3_4_8_2","volume-title":"CLSI supplement M100: peformance standards for antimicrobial susceptibility testing","author":"CLSI","year":"2025","unstructured":"CLSI. 2025. 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