{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,4]],"date-time":"2026-05-04T19:25:22Z","timestamp":1777922722674,"version":"3.51.4"},"reference-count":30,"publisher":"SAGE Publications","issue":"1","license":[{"start":{"date-parts":[[2014,9,4]],"date-time":"2014-09-04T00:00:00Z","timestamp":1409788800000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/journals.sagepub.com\/page\/policies\/text-and-data-mining-license"}],"content-domain":{"domain":["journals.sagepub.com"],"crossmark-restriction":true},"short-container-title":["Microbial Drug Resistance"],"published-print":{"date-parts":[[2015,2,1]]},"abstract":"<jats:p>\n                    Forty-nine clinical\n                    <jats:italic toggle=\"yes\">Escherichia coli<\/jats:italic>\n                    isolates, both extended-spectrum \u03b2-lactamase (ESBL) negative and ESBL positive, were studied to investigate whether increased AmpC expression is a mechanism involved in cefoxitin resistance and if this influences the third-generation cephalosporin activity. Nine of 33 (27.2%) cefoxitin-resistant (minimum inhibitory concentration [MIC] &gt;8\u2009mg\/L) isolates showed hyperproduction of chromosomal AmpC (c-AmpC) based on (1) at least two positive tests using AmpC inhibitors, (2) mutations in the promoter\/attenuator regions, and (3) a 6.1- to 163-fold increase in\n                    <jats:italic toggle=\"yes\">c-ampC<\/jats:italic>\n                    expression by quantitative reverse transcription\u2013polymerase chain reaction. In ESBL-negative isolates, MICs of ceftazidime and cefotaxime were mostly above the wild-type (WT) level, but below the S\/I breakpoint (EUCAST guideline), except for one isolate with MICs of 4\u2009mg\/L. No plasmid-mediated AmpCs were found. Periplasmic extracts of nine c-AmpC hyperproducers were preincubated with or without cefuroxime or ceftazidime and analyzed by sodium dodecyl sulfate\u2013polyacrylamide gel electrophoresis. Cefuroxime and ceftazidime were stable to hydrolysis but acted as inhibitors of the enzyme. None of these isolates showed loss of porins. Thus, cefoxitin resistance has low specificity for detecting upregulated c-AmpC production. c-AmpC hyperproducing\n                    <jats:italic toggle=\"yes\">E. coli<\/jats:italic>\n                    is mostly still susceptible to third-generation cephalosporins but less than WT\n                    <jats:italic toggle=\"yes\">E. coli<\/jats:italic>\n                    . Surveillance of cefoxitin-resistant\n                    <jats:italic toggle=\"yes\">E. coli<\/jats:italic>\n                    to monitor developments in the activity of third-generation cephalosporins against c-AmpC hyperproducers is warranted.\n                  <\/jats:p>","DOI":"10.1089\/mdr.2014.0108","type":"journal-article","created":{"date-parts":[[2014,9,4]],"date-time":"2014-09-04T15:20:50Z","timestamp":1409844050000},"page":"7-16","update-policy":"https:\/\/doi.org\/10.1177\/sage-journals-update-policy","source":"Crossref","is-referenced-by-count":13,"title":["Increased Expression Levels of Chromosomal AmpC \u03b2-Lactamase in Clinical\n                    <i>Escherichia coli<\/i>\n                    Isolates and Their Effect on Susceptibility to Extended-Spectrum Cephalosporins"],"prefix":"10.1177","volume":"21","author":[{"given":"Sunita","family":"Paltansing","sequence":"first","affiliation":[{"name":"Leiden University Medical Center","place":["The Netherlands"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Margriet","family":"Kraakman","sequence":"additional","affiliation":[{"name":"Leiden University Medical Center","place":["The Netherlands"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ria","family":"van Boxtel","sequence":"additional","affiliation":[{"name":"Utrecht University","place":["The Netherlands"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ivo","family":"Kors","sequence":"additional","affiliation":[{"name":"Leiden University Medical Center","place":["The Netherlands"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Els","family":"Wessels","sequence":"additional","affiliation":[{"name":"Leiden University Medical Center","place":["The Netherlands"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Wil","family":"Goessens","sequence":"additional","affiliation":[{"name":"Erasmus University Medical Center","place":["The Netherlands"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jan","family":"Tommassen","sequence":"additional","affiliation":[{"name":"Utrecht University","place":["The Netherlands"]}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Alexandra","family":"Bernards","sequence":"additional","affiliation":[{"name":"Leiden University Medical Center","place":["The Netherlands"]}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"179","published-online":{"date-parts":[[2014,9,4]]},"reference":[{"key":"e_1_3_3_2_2","doi-asserted-by":"publisher","DOI":"10.1021\/bi200403e"},{"key":"e_1_3_3_3_2","doi-asserted-by":"publisher","DOI":"10.1093\/jac\/45.6.783"},{"key":"e_1_3_3_4_2","doi-asserted-by":"publisher","DOI":"10.1093\/jac\/32.suppl_B.63"},{"key":"e_1_3_3_5_2","doi-asserted-by":"publisher","DOI":"10.3201\/eid0910.030093"},{"key":"e_1_3_3_6_2","unstructured":"Clinical Laboratories Standards Institute. 2007. Performance standards for antimicrobial susceptibility testing; Seventeenth Informational Supplement. Clinical Laboratories Standards Institute Wayne PA CLSI document M100-S17 [ISBN1-56238-625-5]."},{"key":"e_1_3_3_7_2","doi-asserted-by":"publisher","DOI":"10.1093\/jac\/dkm284"},{"key":"e_1_3_3_8_2","doi-asserted-by":"publisher","DOI":"10.1016\/S0732-8893(01)00278-4"},{"key":"e_1_3_3_9_2","doi-asserted-by":"publisher","DOI":"10.1128\/AAC.02459-12"},{"key":"e_1_3_3_10_2","doi-asserted-by":"publisher","DOI":"10.1093\/jac\/dkn257"},{"key":"e_1_3_3_11_2","doi-asserted-by":"publisher","DOI":"10.2174\/1381612805666230112191507"},{"key":"e_1_3_3_12_2","doi-asserted-by":"publisher","DOI":"10.1128\/CMR.00036-08"},{"key":"e_1_3_3_13_2","doi-asserted-by":"publisher","DOI":"10.1093\/jac\/dkp484"},{"key":"e_1_3_3_14_2","doi-asserted-by":"publisher","DOI":"10.1089\/mdr.2009.0883"},{"key":"e_1_3_3_15_2","doi-asserted-by":"publisher","DOI":"10.1038\/227680a0"},{"key":"e_1_3_3_16_2","doi-asserted-by":"publisher","DOI":"10.1006\/meth.2001.1262"},{"key":"e_1_3_3_17_2","doi-asserted-by":"publisher","DOI":"10.1128\/AAC.44.5.1387-1390.2000"},{"key":"e_1_3_3_18_2","doi-asserted-by":"publisher","DOI":"10.1128\/AAC.49.1.358-365.2005"},{"key":"e_1_3_3_19_2","doi-asserted-by":"publisher","DOI":"10.1128\/AAC.43.4.957"},{"key":"e_1_3_3_20_2","doi-asserted-by":"publisher","DOI":"10.1128\/AAC.1.4.283"},{"key":"e_1_3_3_21_2","doi-asserted-by":"publisher","DOI":"10.1073\/pnas.80.24.7556"},{"key":"e_1_3_3_22_2","doi-asserted-by":"publisher","DOI":"10.1016\/S0021-9258(19)45128-4"},{"key":"e_1_3_3_23_2","doi-asserted-by":"publisher","DOI":"10.1097\/QCO.0b013e3283398dc1"},{"key":"e_1_3_3_24_2","doi-asserted-by":"publisher","DOI":"10.1128\/JCM.40.6.2153-2162.2002"},{"key":"e_1_3_3_25_2","doi-asserted-by":"publisher","DOI":"10.1128\/JCM.00091-11"},{"key":"e_1_3_3_26_2","doi-asserted-by":"publisher","DOI":"10.1128\/AAC.01004-09"},{"key":"e_1_3_3_27_2","doi-asserted-by":"publisher","DOI":"10.1128\/AAC.47.7.2138-2144.2003"},{"key":"e_1_3_3_28_2","doi-asserted-by":"publisher","DOI":"10.1128\/AAC.21.5.711"},{"key":"e_1_3_3_29_2","doi-asserted-by":"publisher","DOI":"10.1002\/j.1460-2075.1983.tb01581.x"},{"key":"e_1_3_3_30_2","doi-asserted-by":"publisher","DOI":"10.1111\/j.1574-6968.2007.00672.x"},{"key":"e_1_3_3_31_2","doi-asserted-by":"publisher","DOI":"10.1126\/science.1078973"}],"container-title":["Microbial Drug Resistance"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/journals.sagepub.com\/doi\/full-xml\/10.1089\/mdr.2014.0108","content-type":"application\/xml","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/journals.sagepub.com\/doi\/pdf\/10.1089\/mdr.2014.0108","content-type":"application\/pdf","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/journals.sagepub.com\/doi\/pdf\/10.1089\/mdr.2014.0108","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,5,1]],"date-time":"2026-05-01T20:28:45Z","timestamp":1777667325000},"score":1,"resource":{"primary":{"URL":"https:\/\/journals.sagepub.com\/doi\/10.1089\/mdr.2014.0108"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2014,9,4]]},"references-count":30,"journal-issue":{"issue":"1","published-print":{"date-parts":[[2015,2,1]]}},"alternative-id":["10.1089\/mdr.2014.0108"],"URL":"https:\/\/doi.org\/10.1089\/mdr.2014.0108","relation":{},"ISSN":["1076-6294","1931-8448"],"issn-type":[{"value":"1076-6294","type":"print"},{"value":"1931-8448","type":"electronic"}],"subject":[],"published":{"date-parts":[[2014,9,4]]}}}