title: Transposition of ISEcp1 modulates blaCTX-M-55-mediated Shigella flexneri resistance to cefalothin.
abstract: The aim of this study was to uncover the mechanisms underlying Shigella flexneri resistance to cefalothin. In this study, a resistance-related S. flexneri isolate, S. flexneri YDC, was obtained from S. flexneri mel-1998023/zz pre-incubated with cefalothin at a dose of 0.5 × the minimum inhibitory concentration. The ISEcp1 coding element was identified upstream of bla(CTX-M-55) in S. flexneri YDC. To further determine the role of ISEcp1 in S. flexneri resistance, plasmids containing bla(CTX-M-55) recombinant with or without the ISEcp1 sequence were constructed and named as pCTX and pISECTX, respectively. It was shown that Escherichia coli DH5α(pISECTX) was resistant to all β-lactams tested. In contrast, E. coli DH5α(pCTX) was sensitive to all except β-lactams cefazolin and cefalothin. In addition, reverse transcription PCR showed that expression levels of bla(CTX-M-55) were higher in E. coli DH5α(pISECTX). The Clinical and Laboratory Standards Institute (CLSI) assay demonstrated that extended-spectrum β-lactamase was only positively detected in E. coli DH5α(pISECTX) but not in E. coli DH5α(pCTX). Taken together, these results suggest that the translocated ISEcp1 element upstream of bla(CTX-M-55) is required for overexpression of bla(CTX-M-55), leading to cephalosporin resistance.
authors.affiliation: Department of Epidemiology, College of Public Health, Zhengzhou University, Zhengzhou, Henan, PR China; Henan University of Science and Technology, Luoyang, Henan, PR China.
authors.forename: Yingfang
authors.initials: Y
authors.lastname: Wang
authors.forename: Chunhua
authors.initials: C
authors.lastname: Song
authors.forename: Guangcai
authors.initials: G
authors.lastname: Duan
authors.forename: Jingyuan
authors.initials: J
authors.lastname: Zhu
authors.forename: Haiyan
authors.initials: H
authors.lastname: Yang
authors.forename: Yuanlin
authors.initials: Y
authors.lastname: Xi
authors.forename: Qingtang
authors.initials: Q
authors.lastname: Fan
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002512:Cephalothin / Q000494:pharmacology*; D004251:DNA Transposable Elements; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D011995:Recombination, Genetic; D017422:Sequence Analysis, DNA; D012763:Shigella flexneri / Q000187:drug effects* / Q000235:genetics; D018440:beta-Lactam Resistance; D001618:beta-Lactamases / Q000235:genetics*
chemical_list: D000900:Anti-Bacterial Agents; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D001618:beta-Lactamases; D002512:Cephalothin
keywords: Extended-spectrum β-lactamase; ISEcp1; bla(CTX-M-55)