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PLoS One. 2010 Jun 18;5(6):e11202. doi: 10.1371/journal.pone.0011202.

Complete nucleotide sequence of CTX-M-15-plasmids from clinical Escherichia coli isolates: insertional events of transposons and insertion sequences.

Author information

1
Department of Pathology, Bacteriology and Avian Diseases, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium. Annemieke.Smet@UGent.be

Abstract

BACKGROUND:

CTX-M-producing Escherichia coli strains are regarded as major global pathogens.

METHODOLOGY/PRINCIPAL FINDINGS:

The nucleotide sequence of three plasmids (pEC_B24: 73801-bp; pEC_L8: 118525-bp and pEC_L46: 144871-bp) from Escherichia coli isolates obtained from patients with urinary tract infections and one plasmid (pEC_Bactec: 92970-bp) from an Escherichia coli strain isolated from the joint of a horse with arthritis were determined. Plasmid pEC_Bactec belongs to the IncI1 group and carries two resistance genes: bla(TEM-1) and bla(CTX-M-15). It shares more than 90% homology with a previously published bla(CTX-M)-plasmid from E. coli of human origin. Plasmid pEC_B24 belongs to the IncFII group whereas plasmids pEC_L8 and pEC_L46 represent a fusion of two replicons of type FII and FIA. On the pEC_B24 backbone, two resistance genes, bla(TEM-1) and bla(CTX-M-15), were found. Six resistance genes, bla(TEM-1), bla(CTX-M-15), bla(OXA-1), aac6'-lb-cr, tetA and catB4, were detected on the pEC_L8 backbone. The same antimicrobial drug resistance genes, with the exception of tetA, were also identified on the pEC_L46 backbone. Genome analysis of all 4 plasmids studied provides evidence of a seemingly frequent transposition event of the bla(CTX-M-15)-ISEcp1 element. This element seems to have a preferred insertion site at the tnpA gene of a bla(TEM)-carrying Tn3-like transposon, the latter itself being inserted by a transposition event. The IS26-composite transposon, which contains the bla(OXA-1), aac6'-lb-cr and catB4 genes, was inserted into plasmids pEC_L8 and pEC_L46 by homologous recombination rather than a transposition event. Results obtained for pEC_L46 indicated that IS26 also plays an important role in structural rearrangements of the plasmid backbone and seems to facilitate the mobilisation of fragments from other plasmids.

CONCLUSIONS:

Collectively, these data suggests that IS26 together with ISEcp1 could play a critical role in the evolution of diverse multiresistant plasmids found in clinical Enterobacteriaceae.

PMID:
20585456
PMCID:
PMC2887853
DOI:
10.1371/journal.pone.0011202
[Indexed for MEDLINE]
Free PMC Article
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