{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,13]],"date-time":"2026-10-13T03:18:59Z","timestamp":1791861539063,"version":"4.3.4"},"reference-count":20,"publisher":"Oxford University Press (OUP)","issue":"11","license":[{"start":{"date-parts":[[2019,8,14]],"date-time":"2019-08-14T00:00:00Z","timestamp":1565740800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/academic.oup.com\/journals\/pages\/open_access\/funder_policies\/chorus\/standard_publication_model"}],"funder":[{"DOI":"10.13039\/501100006197","name":"Fonden til L\u00e6gevidenskabens Fremme","doi-asserted-by":"crossref","award":["17-L-0495"],"award-info":[{"award-number":["17-L-0495"]}],"id":[{"id":"10.13039\/501100006197","id-type":"DOI","asserted-by":"crossref"}]},{"name":"Scandinavian Society of Antimicrobial Chemotherapy Foundation","award":["SLS-788501"],"award-info":[{"award-number":["SLS-788501"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2019,11,1]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:sec><jats:title>Background<\/jats:title><jats:p>bla TEM-1 encodes a narrow-spectrum \u03b2-lactamase that is inhibited by \u03b2-lactamase inhibitors and commonly present in Escherichia coli. Hyperproduction of blaTEM-1 may cause resistance to penicillin\/\u03b2-lactamase inhibitor (P\/BLI) combinations.<\/jats:p><\/jats:sec><jats:sec><jats:title>Objectives<\/jats:title><jats:p>To characterize EC78, an E. coli bloodstream isolate, resistant to P\/BLI combinations, which contains extensive amplification of blaTEM-1 within the chromosome.<\/jats:p><\/jats:sec><jats:sec><jats:title>Methods<\/jats:title><jats:p>EC78 was sequenced using Illumina and Oxford Nanopore Technology (ONT) methodology. Configuration of blaTEM-1 amplification was probed using PCR. Expression of blaTEM-1 mRNA was determined using quantitative PCR and \u03b2-lactamase activity was determined spectrophotometrically in a nitrocefin conversion assay. Growth rate was assessed to determine fitness and stability of the gene amplification was assessed by passage in the absence of antibiotics.<\/jats:p><\/jats:sec><jats:sec><jats:title>Results<\/jats:title><jats:p>Illumina sequencing of EC78 identified blaTEM-1B as the only acquired \u03b2-lactamase preceded by the WT P3 promoter and present at a copy number of 182.6 with blaTEM-1B bracketed by IS26 elements. The chromosomal location of the IS26-blaTEM-1B amplification was confirmed by ONT sequencing. Hyperproduction of blaTEM-1 was confirmed by increased transcription of blaTEM-1 and \u03b2-lactamase activity and associated with a significant fitness cost; however, the array was maintained at a relatively high copy number for 150 generations. PCR screening for blaTEM amplification of isolates resistant to P\/BLI combinations identified an additional strain containing an IS26-associated amplification of a blaTEM gene.<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusions<\/jats:title><jats:p>IS26-associated amplification of blaTEM can cause resistance to P\/BLI combinations. This adaptive mechanism of resistance may be overlooked if simple methods of genotypic prediction (e.g. gene presence\/absence) are used to predict antimicrobial susceptibility from sequencing data.<\/jats:p><\/jats:sec>","DOI":"10.1093\/jac\/dkz349","type":"journal-article","created":{"date-parts":[[2019,7,24]],"date-time":"2019-07-24T11:25:50Z","timestamp":1563967550000},"page":"3179-3183","source":"Crossref","is-referenced-by-count":67,"title":["Resistance to piperacillin\/tazobactam in Escherichia coli resulting from extensive IS26-associated gene amplification of blaTEM-1"],"prefix":"10.1093","volume":"74","author":[{"given":"Katrine Hartung","family":"Hansen","sequence":"first","affiliation":[{"name":"Department of Clinical Microbiology 445, Hvidovre University Hospital, Hvidovre, Denmark"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Minna Rud","family":"Andreasen","sequence":"additional","affiliation":[{"name":"Department of Clinical Microbiology 445, Hvidovre 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