title: Effect of spacer sequences between bla(CTX-M) and ISEcp1 on bla(CTX-M) expression.
abstract: Spacer sequences of 42 and 127 bp, respectively, between the ISEcp1 insertion sequence and bla(CTX-M) have been observed in Klebsiella pneumoniae. However, it is not known whether different spacers upstream of bla(CTX-M) and a promoter within the 127 bp spacer influence cephalosporin resistance. Three recombinant plasmids with different spacers and with or without ISEcp1 were constructed to compare bla(CTX-M-3) expression and susceptibility to cephalosporins. Our experiment revealed enhanced bla(CTX-M-3) expression and a relatively high level resistance to cefotaxime and cefepime in recombinant plasmid IS42CTX-M-3, which contained ISEcp1 and the 42 bp spacer. A minor difference in bla(CTX-M-3) expression was observed in recombinants IS127CTX-M-3 and 127CTX-M-3, which contained a 127 bp spacer with or without ISEcp1, respectively. In conclusion, the promoter within ISEcp1 and a shorter spacer (42 bp but not 127 bp) between ISEcp1 and bla(CTX-M) are necessary for high-level bla(CTX-M-3) expression.
authors.affiliation: Division of Infectious Disease, National Health Research Institutes, Miaoli County, Taiwan, ROC.
authors.forename: Ling
authors.initials: L
authors.lastname: Ma
authors.affiliation: Division of Infectious Disease, National Health Research Institutes, Miaoli County, Taiwan, ROC.
authors.forename: Leung Kris
authors.initials: LK
authors.lastname: Siu
authors.affiliation: School of Medicine, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Taiwan, ROC.|Department of Internal Medicine and Laboratory Medicine, Kaohsiung Medical University Hospital, Kaohsiung Medical University, Taiwan, ROC.
authors.forename: Po-Liang
authors.initials: PL
authors.lastname: Lu
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D000077723:Cefepime; D002439:Cefotaxime / Q000494:pharmacology; D018550:Cephalosporin Resistance / Q000235:genetics*; D002511:Cephalosporins / Q000494:pharmacology; D004251:DNA Transposable Elements; D021901:DNA, Intergenic / Q000235:genetics; D015870:Gene Expression; D007711:Klebsiella pneumoniae / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D010957:Plasmids; D011401:Promoter Regions, Genetic; D012329:RNA, Bacterial / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001618:beta-Lactamases / Q000096:biosynthesis / Q000235:genetics*
chemical_list: D000900:Anti-Bacterial Agents; D002511:Cephalosporins; D004251:DNA Transposable Elements; D021901:DNA, Intergenic; D012329:RNA, Bacterial; D012333:RNA, Messenger; D000077723:Cefepime; C417271:beta-lactamase CTX-M-3; D001618:beta-Lactamases; D002439:Cefotaxime