Dataset Information

Closely related NDM-1-encoding plasmids from Escherichia coli and Klebsiella pneumoniae in Taiwan.

ABSTRACT:

Objective

Two plasmids carrying blaNDM-1 isolated from carbapenem-resistant Klebsiella pneumoniae (CR-KP) and carbapenem-resistant Escherichia coli (CR-EC) were sequenced. CR-KP and CR-EC were isolated from two Taiwanese patients without travel histories.

Methods

Complete sequencing of the plasmids (pLK75 and pLK78) was conducted using a shotgun approach. Annotation of the contigs was performed using the RAST Server, followed by manual inspection and correction.

Results

These similar plasmids were obtained from two patients with overlapping stays at the same hospital. The pLK75 and pLK78 plasmids were 56,489-bp and 56,072-bp in length, respectively. Plasmid annotation revealed a common backbone similar to the IncN plasmid pR46. The regions flanking the blaNDM-1 genes in these plasmids were very similar to plasmid pNDM-HU01 in Japan, which contains a complex class 1 integron located next to an ISCR1 element. The ISCR1 element has been suggested to provide a powerful mechanism for mobilising antibiotic resistance genes.

Conclusion

Two indigenous NDM-1-producing Enterobacteriaceae cases were identified for the first time in Taiwan, highlighting the alarming introduction of NDM-1-producing Enterobacteriaceae in this region.

SUBMITTER: Chen CJ

PROVIDER: S-EPMC4140731 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Project description:Multidrug-resistant Enterobacteriaceae are emerging as a serious infectious disease challenge. These strains can accumulate many antibiotic resistance genes though horizontal transfer of genetic elements, those for β-lactamases being of particular concern. Some β-lactamases are active on a broad spectrum of β-lactams including the last-resort carbapenems. The gene for the broad-spectrum and carbapenem-active metallo-β-lactamase NDM-1 is rapidly spreading. We present the complete genome of Klebsiella pneumoniae ATCC BAA-2146, the first U.S. isolate found to encode NDM-1, and describe its repertoire of antibiotic-resistance genes and mutations, including genes for eight β-lactamases and 15 additional antibiotic-resistance enzymes. To elucidate the evolution of this rich repertoire, the mobile elements of the genome were characterized, including four plasmids with varying degrees of conservation and mosaicism and eleven chromosomal genomic islands. One island was identified by a novel phylogenomic approach, that further indicated the cps-lps polysaccharide synthesis locus, where operon translocation and fusion was noted. Unique plasmid segments and mosaic junctions were identified. Plasmid-borne blaCTX-M-15 was transposed recently to the chromosome by ISEcp1. None of the eleven full copies of IS26, the most frequent IS element in the genome, had the expected 8-bp direct repeat of the integration target sequence, suggesting that each copy underwent homologous recombination subsequent to its last transposition event. Comparative analysis likewise indicates IS26 as a frequent recombinational junction between plasmid ancestors, and also indicates a resolvase site. In one novel use of high-throughput sequencing, homologously recombinant subpopulations of the bacterial culture were detected. In a second novel use, circular transposition intermediates were detected for the novel insertion sequence ISKpn21 of the ISNCY family, suggesting that it uses the two-step transposition mechanism of IS3. Robust genome-based phylogeny showed that a unified Klebsiella cluster contains Enterobacter aerogenes and Raoultella, suggesting the latter genus should be abandoned.