ColE1-Like Plasmid pIP843 of Klebsiella pneumoniae Encoding Extended-Spectrum β-Lactamase CTX-M-17

Abstract

ABSTRACT The resistance of Klebsiella pneumoniae BM4493, isolated in Ho Chi Minh City, Vietnam, to cefotaxime and aztreonam was due to production of a novel β-lactamase, CTX-M-17. The bla CTX-M-17 gene was borne by 7,086-bp plasmid pIP843, which was entirely sequenced and which was found to belong to the ColE1 family. The 876-bp bla CTX-M-17 gene differed from bla CTX-M-14 by 2 nucleotides, which led to the single amino acid substitution Glu289→Lys. bla CTX-M-17 was flanked upstream by an IS Ecp1 -like element and downstream by an insertion sequence (IS) IS 903 variant designated IS 903 -C. The transcriptional start site of bla CTX-M-17 was located 109 nucleotides upstream from the initiation codon in the IS Ecp1- like element, which also provided the promoter sequences. Plasmid pIP843, which was non-self-transferable and nonmobilizable, contained five open reading frames transcribed in the same orientation. Regions homologous to sequences coding for putative RNA II and RNA I transcripts, a rom gene, which is involved in initiation of replication, and a cer -like gene, which is responsible for the stability of ColE1-like plasmids, were identified. Consensus sequences for putative replication ( oriV ) and transfer ( oriT ) origins were present. Results of primer extension experiments indicated that IS Ecp1 provides the promoter for expression of bla CTX-M-17 and may contribute to dissemination of this gene.