{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,21]],"date-time":"2026-10-21T23:11:00Z","timestamp":1792624260961,"version":"4.5.0"},"reference-count":18,"publisher":"Oxford University Press (OUP)","issue":"5","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2015,5,1]]},"abstract":"<jats:title>Abstract<\/jats:title>\n               <jats:sec>\n                  <jats:title>Objectives<\/jats:title>\n                  <jats:p>Klebsiella oxytoca is a member of the family of Enterobacteriaceae and often contains the \u03b2-lactamase blaOXY gene. Although this \u03b2-lactamase does not naturally hydrolyse ceftazidime, this study describes possible in vivo selection of a clinical K. oxytoca isolate showing increased MICs of ceftazidime.<\/jats:p>\n               <\/jats:sec>\n               <jats:sec>\n                  <jats:title>Methods<\/jats:title>\n                  <jats:p>To reveal the molecular mechanism underlying this unusual resistance phenotype, WGS, cloning, overexpression, MIC and steady-state kinetic studies were performed.<\/jats:p>\n               <\/jats:sec>\n               <jats:sec>\n                  <jats:title>Results<\/jats:title>\n                  <jats:p>A patient was treated for a septic episode with ceftazidime (4 g\/day). This therapy was based on earlier culture results in which, amongst others, a K. oxytoca (Velp-1) isolate was identified. After 11 days of treatment, K. oxytoca Velp-2 was isolated from a pus sample drained from the wound. The isolate showed increased resistance to ceftazidime (MIC \u226564 mg\/L) compared with the original K. oxytoca isolate (Velp-1). WGS revealed the presence of a novel blaOXY-2 allele, designated blaOXY-2-15, with a two amino acid deletion at Ambler positions 168 and 169 compared with OXY-2-2. Cloning blaOXY-2-15 into Escherichia coli TOP10 resulted in increased MICs of ceftazidime, but reduced MICs of most other \u03b2-lactams compared with OXY-2-2. Steady-state kinetics confirmed the results of the MIC data, showing clearly significant ceftazidime hydrolysis.<\/jats:p>\n               <\/jats:sec>\n               <jats:sec>\n                  <jats:title>Conclusions<\/jats:title>\n                  <jats:p>This report shows the risk of in vivo selection of ceftazidime-resistant K. oxytoca isolates after prolonged ceftazidime treatment. Furthermore, it is the first known report of a K. oxytoca isolate conferring resistance to ceftazidime by a two amino acid deletion in the omega loop of OXY-2-2.<\/jats:p>\n               <\/jats:sec>","DOI":"10.1093\/jac\/dkv002","type":"journal-article","created":{"date-parts":[[2015,1,29]],"date-time":"2015-01-29T04:31:38Z","timestamp":1422505898000},"page":"1429-1433","source":"Crossref","is-referenced-by-count":26,"title":["OXY-2-15, a novel variant showing increased ceftazidime hydrolytic activity"],"prefix":"10.1093","volume":"70","author":[{"given":"R. H. T.","family":"Nijhuis","sequence":"first","affiliation":[{"name":"1 \u00a0Laboratory for Medical Microbiology and Immunology, Rijnstate, Velp, The Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"S.","family":"Oueslati","sequence":"additional","affiliation":[{"name":"2 \u00a0Bact\u00e9riologie-Virologie, AP-HP, LabEx LERMIT, Univ. Paris-Sud, Paris, France"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"K.","family":"Zhou","sequence":"additional","affiliation":[{"name":"3 \u00a0Molecular Unit, Department of Medical Microbiology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"R. W.","family":"Bosboom","sequence":"additional","affiliation":[{"name":"1 \u00a0Laboratory for Medical Microbiology and Immunology, Rijnstate, Velp, The Netherlands"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"J. W. 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