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

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 ISEcp1-like element and downstream by an insertion sequence (IS) IS903 variant designated IS903-C. The transcriptional start site of bla_CTX-M-17 was located 109 nucleotides upstream from the initiation codon in the ISEcp1-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 ISEcp1 provides the promoter for expression of bla_CTX-M-17 and may contribute to dissemination of this gene.