{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,12]],"date-time":"2026-08-12T04:06:10Z","timestamp":1786507570139,"version":"build-2736575974"},"reference-count":20,"publisher":"Oxford University Press (OUP)","issue":"7","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2015,7,1]]},"abstract":"<jats:title>Abstract<\/jats:title>\n               <jats:sec>\n                  <jats:title>Objectives<\/jats:title>\n                  <jats:p>Escherichia coli ST131 is a globally disseminated MDR clone originally identified due to its association with the blaCTX-M-15 gene encoding an ESBL. It is thus assumed that blaCTX-M-15 is the major determinant for resistance to \u03b2-lactam antibiotics in this clone. The complete sequence of EC958, a reference strain for E. coli ST131, revealed that it contains a chromosomally located blaCMY-23 gene with an upstream ISEcp1 element as well as several additional plasmid-encoded \u03b2-lactamase genes. Here, we examined the genetic context of the blaCMY-23 element in EC958 and other E. coli ST131 strains and investigated the contribution of blaCMY-23 to EC958 resistance to a range of \u03b2-lactam antibiotics.<\/jats:p>\n               <\/jats:sec>\n               <jats:sec>\n                  <jats:title>Methods<\/jats:title>\n                  <jats:p>The genetic context of blaCMY-23 and its associated mobile elements was determined by PCR and sequencing. Antibiotic susceptibility testing was performed using Etests. The activity of the blaCMY-23 promoter was assessed using lacZ reporter assays. Mutations were generated using \u03bb-Red-recombination.<\/jats:p>\n               <\/jats:sec>\n               <jats:sec>\n                  <jats:title>Results<\/jats:title>\n                  <jats:p>The genetic structure of the ISEcp1-IS5-blaCMY-23 mobile element was determined and localized within the betU gene on the chromosome of EC958 and five other E. coli ST131 strains. The transcription of blaCMY-23, driven by a previously defined promoter within ISEcp1, was significantly higher than other \u03b2-lactamase genes and could be induced by cefotaxime. Deletion of the blaCMY-23 gene resulted in enhanced susceptibility to cefoxitin, cefotaxime and ceftazidime.<\/jats:p>\n               <\/jats:sec>\n               <jats:sec>\n                  <jats:title>Conclusions<\/jats:title>\n                  <jats:p>This is the first known report to demonstrate the chromosomal location of blaCMY-23 in E. coli ST131. In EC958, CMY-23 plays a major role in resistance to third-generation cephalosporins and cephamycins.<\/jats:p>\n               <\/jats:sec>","DOI":"10.1093\/jac\/dkv066","type":"journal-article","created":{"date-parts":[[2015,3,19]],"date-time":"2015-03-19T00:51:58Z","timestamp":1426726318000},"page":"1969-1972","source":"Crossref","is-referenced-by-count":16,"title":["Third-generation cephalosporin resistance conferred by a chromosomally encoded <i>bla<\/i>CMY-23 gene in the <i>Escherichia coli<\/i> ST131 reference strain EC958"],"prefix":"10.1093","volume":"70","author":[{"given":"Minh-Duy","family":"Phan","sequence":"first","affiliation":[{"name":"1 \u00a0Australian Infectious Diseases Research Centre, School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD 4072, Australia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Kate M.","family":"Peters","sequence":"additional","affiliation":[{"name":"1 \u00a0Australian Infectious Diseases Research Centre, School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD 4072, Australia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Sohinee","family":"Sarkar","sequence":"additional","affiliation":[{"name":"1 \u00a0Australian Infectious Diseases Research Centre, School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD 4072, Australia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Brian M.","family":"Forde","sequence":"additional","affiliation":[{"name":"1 \u00a0Australian Infectious Diseases Research Centre, School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD 4072, Australia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Alvin W.","family":"Lo","sequence":"additional","affiliation":[{"name":"1 \u00a0Australian Infectious Diseases Research Centre, School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD 4072, Australia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mitchell","family":"Stanton-Cook","sequence":"additional","affiliation":[{"name":"1 \u00a0Australian Infectious Diseases Research Centre, School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD 4072, Australia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Leah W.","family":"Roberts","sequence":"additional","affiliation":[{"name":"1 \u00a0Australian Infectious Diseases Research Centre, School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD 4072, Australia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mathew","family":"Upton","sequence":"additional","affiliation":[{"name":"2 \u00a0Plymouth University Peninsula Schools of Medicine and Dentistry, Plymouth PL4 8AA, UK"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Scott A.","family":"Beatson","sequence":"additional","affiliation":[{"name":"1 \u00a0Australian Infectious Diseases Research Centre, School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD 4072, Australia"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mark A.","family":"Schembri","sequence":"additional","affiliation":[{"name":"1 \u00a0Australian Infectious Diseases Research Centre, School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD 4072, Australia"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"286","published-online":{"date-parts":[[2015,3,18]]},"reference":[{"key":"2022020121023455100_DKV066C1","doi-asserted-by":"crossref","first-page":"273","DOI":"10.1093\/jac\/dkm464","article-title":"Intercontinental emergence of Escherichia coli clone O25:H4-ST131 producing CTX-M-15","volume":"61","author":"Nicolas-Chanoine","year":"2008","journal-title":"J Antimicrob 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