{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,6]],"date-time":"2026-10-06T17:49:24Z","timestamp":1791308964855,"version":"4.3.1"},"reference-count":32,"publisher":"American Society for Microbiology","issue":"1","license":[{"start":{"date-parts":[[2014,1,1]],"date-time":"2014-01-01T00:00:00Z","timestamp":1388534400000},"content-version":"tdm","delay-in-days":0,"URL":"https:\/\/journals.asm.org\/non-commercial-tdm-license"}],"content-domain":{"domain":["journals.asm.org"],"crossmark-restriction":true},"short-container-title":["J Clin Microbiol"],"published-print":{"date-parts":[[2014,1]]},"abstract":"<jats:title>ABSTRACT<\/jats:title><jats:p>Under the auspices of the Spanish Society for Infectious Diseases and Clinical Microbiology Quality Control program, 14<jats:named-content content-type=\"genus-species\">Escherichia coli<\/jats:named-content>strains masked as blood culture isolates were sent to 68 clinical microbiology laboratories for antimicrobial susceptibility testing to \u03b2-lactam antibiotics. This collection included three control strains (<jats:named-content content-type=\"genus-species\">E. coli<\/jats:named-content>ATCC 25922, an IRT-2 producer, and a CMY-2 producer), six isogenic strains with or without the OmpF porin and expressing CTX-M \u03b2-lactamases (CTX-M-1, CTX-M-15, and CTX-M-14), one strain carrying a double mechanism for \u03b2-lactam resistance (i.e., carrying CTX-M-15 and OXA-1 enzymes), and four strains carrying CTX-M variants with different levels of resistance to \u03b2-lactams and \u03b2-lactam\u2013\u03b2-lactamase inhibitor (BLBLI) combinations. The main objective of the study was to ascertain how these variants with reduced susceptibilities to BLBLIs are identified in clinical microbiology laboratories. CTX-M variants with high resistance to BLBLIs were mainly identified as inhibitor-resistant TEM (IRT) enzymes (68.0%); however, isogenic CTX-M mutant strains with reduced susceptibilities to BLBLIs and cephalosporins were mainly associated with extended-spectrum \u03b2-lactamase production alone (51 to 80%) or in combination with other mechanisms (14 to 31%). Concerning all \u03b2-lactams tested, the overall interpretative discrepancy rate was 11.5%, of which 38.1% were the consequence of postreading changes in the clinical categories when a resistance mechanism was inferred. Therefore, failure to recognize these complex phenotypes might contribute to an explanation of their apparent absence in the clinical setting and might lead to inadequate drug treatment selection. A proposal for improving recognition is to adhere strictly to the current CLSI or EUCAST guidelines for detecting reduced susceptibility to BLBLI combinations, without any interpretative modification.<\/jats:p>","DOI":"10.1128\/jcm.02340-13","type":"journal-article","created":{"date-parts":[[2013,10,24]],"date-time":"2013-10-24T03:09:23Z","timestamp":1382584163000},"page":"122-129","update-policy":"https:\/\/doi.org\/10.1128\/asmj-crossmark-policy-page","source":"Crossref","is-referenced-by-count":23,"title":["Detection of Resistance to Beta-Lactamase Inhibitors in Strains with CTX-M Beta-Lactamases: a Multicenter External Proficiency Study Using a Well-Defined Collection of Escherichia coli Strains"],"prefix":"10.1128","volume":"52","author":[{"given":"Aida","family":"Ripoll","sequence":"first","affiliation":[{"name":"Servicio de Microbiolog\u00eda, Hospital Ram\u00f3n y Cajal and Instituto de Investigaci\u00f3n Sanitaria (IRYCIS), Madrid, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Juan-Carlos","family":"Gal\u00e1n","sequence":"additional","affiliation":[{"name":"Servicio de Microbiolog\u00eda, Hospital Ram\u00f3n y Cajal and Instituto de Investigaci\u00f3n Sanitaria (IRYCIS), Madrid, Spain"},{"name":"CIBER en Epidemiologia y Salud P\u00fablica (CIBERESP) Instituto de Salud Carlos III, Madrid, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Cristina","family":"Rodr\u00edguez","sequence":"additional","affiliation":[{"name":"Servicio de Microbiolog\u00eda, Hospital Universitario Marqu\u00e9s de Valdecilla-IFIMAV, Santander, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Nuria","family":"Tormo","sequence":"additional","affiliation":[{"name":"Servicio de Microbiolog\u00eda, Hospital General de Valencia, Valencia, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Concepci\u00f3n","family":"Gimeno","sequence":"additional","affiliation":[{"name":"Servicio de Microbiolog\u00eda, Hospital General de Valencia, Valencia, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Fernando","family":"Baquero","sequence":"additional","affiliation":[{"name":"Servicio de Microbiolog\u00eda, Hospital Ram\u00f3n y Cajal and Instituto de Investigaci\u00f3n Sanitaria (IRYCIS), Madrid, Spain"},{"name":"CIBER en Epidemiologia y Salud P\u00fablica (CIBERESP) Instituto de Salud Carlos III, Madrid, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Luis","family":"Mart\u00ednez-Mart\u00ednez","sequence":"additional","affiliation":[{"name":"Servicio de Microbiolog\u00eda, Hospital Universitario Marqu\u00e9s de Valdecilla-IFIMAV, Santander, Spain"},{"name":"Departamento de Biolog\u00eda Molecular, Universidad de Cantabria, Santander, Spain"},{"name":"Spanish Network for the Research in Infectious Diseases (REIPI), Instituto de Salud Carlos III, Madrid, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Rafael","family":"Cant\u00f3n","sequence":"additional","affiliation":[{"name":"Servicio de Microbiolog\u00eda, Hospital Ram\u00f3n y Cajal and Instituto de Investigaci\u00f3n Sanitaria (IRYCIS), Madrid, Spain"},{"name":"Spanish Network for the Research in Infectious Diseases (REIPI), Instituto de Salud Carlos III, Madrid, Spain"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"235","reference":[{"key":"e_1_3_3_2_2","doi-asserted-by":"publisher","DOI":"10.1056\/NEJMra041359"},{"key":"e_1_3_3_3_2","doi-asserted-by":"publisher","DOI":"10.3201\/eid1402.070350"},{"key":"e_1_3_3_4_2","doi-asserted-by":"publisher","DOI":"10.1093\/jac\/dkl483"},{"key":"e_1_3_3_5_2","doi-asserted-by":"publisher","DOI":"10.1016\/S1473-3099(08)70041-0"},{"key":"e_1_3_3_6_2","doi-asserted-by":"publisher","DOI":"10.1128\/AAC.00178-11"},{"key":"e_1_3_3_7_2","doi-asserted-by":"publisher","DOI":"10.1128\/AAC.06393-11"},{"key":"e_1_3_3_8_2","doi-asserted-by":"publisher","DOI":"10.2165\/11533040-000000000-00000"},{"key":"e_1_3_3_9_2","doi-asserted-by":"publisher","DOI":"10.1093\/cid\/cir790"},{"key":"e_1_3_3_10_2","doi-asserted-by":"publisher","DOI":"10.1111\/j.1469-0691.2007.01849.x"},{"key":"e_1_3_3_11_2","doi-asserted-by":"publisher","DOI":"10.1128\/AEM.66.3.943-947.2000"},{"key":"e_1_3_3_12_2","doi-asserted-by":"publisher","DOI":"10.1128\/jb.177.1.103-113.1995"},{"key":"e_1_3_3_13_2","doi-asserted-by":"publisher","DOI":"10.1128\/JCM.00608-10"},{"key":"e_1_3_3_14_2","doi-asserted-by":"publisher","DOI":"10.1007\/s10096-012-1737-0"},{"key":"e_1_3_3_15_2","volume-title":"Methods for dilution antimicrobial susceptibility testing for bacteria that grow aerobically; approved standard\u2014","author":"Clinical and Laboratory Standards Institute","year":"2012","unstructured":"Clinical and Laboratory Standards Institute. 2012. 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