Showing papers by "Laura Villa published in 2012"
TL;DR: A carbapenemase-resistant Klebsiella pneumoniae strain, clone ST258 producing KPC-3, was fully characterized, carrying a formidable set of resistance genes against toxic compounds, metals, and antimicrobial drugs and a novel iron(III) uptake system.
Abstract: A carbapenemase-resistant Klebsiella pneumoniae strain, clone ST258 producing KPC-3, was fully characterized. The entire plasmid content was investigated, thereby identifying plasmids of the IncFIIk (two of them similar to pKPQIL and pKPN3, respectively), IncX, and ColE types, carrying a formidable set of resistance genes against toxic compounds, metals, and antimicrobial drugs and a novel iron(III) uptake system.
169 citations
TL;DR: Comparative analysis showed that the blaNDM-1 gene was located on a widely diffused plasmid scaffold known to be responsible for the spread of blaCMY-2-like genes and consequently for resistance to broad-spectrum cephalosporins.
Abstract: The bla(NDM-1) gene has been reported to be often located on broad-host-range plasmids of the IncA/C type in clinical but also environmental bacteria recovered from the New Delhi, India, area. IncA/C-type plasmids are the main vehicles for the spread of the cephalosporinase gene bla(CMY-2), frequently identified in the United States, Canada, and Europe. In this study, we completed the sequence of IncA/C plasmid pNDM-KN carrying the bla(NDM-1) gene, recovered from a Klebsiella pneumoniae isolate from Kenya. This sequence was compared with those of three IncA/C-type reference plasmids from Escherichia coli, Yersinia ruckeri, and Photobacterium damselae. Comparative analysis showed that the bla(NDM-1) gene was located on a widely diffused plasmid scaffold known to be responsible for the spread of bla(CMY-2)-like genes and consequently for resistance to broad-spectrum cephalosporins. Considering that IncA/C plasmids possess a broad host range, this scaffold might support a large-scale diffusion of the bla(NDM-1) gene among Gram-negative rods.
118 citations
TL;DR: This study underlines the diversity of genetic vehicles involved in the spread of the bla(NDM-1) gene and identifies a novel plasmid type within the IncH plasmids family.
Abstract: Methods: The plasmid DNA sequence was obtained by using the 454-Genome Sequencer FLX procedure on a library constructed from total plasmid DNA obtained from an Escherichia coli J53 transconjugant. Contig assembly and predicted gaps were confirmed and filled by PCR-based gap closure. Results: Plasmid pNDM-MAR was 267242 bp long and encoded 177 predicted proteins. It harboured novel replicons and transfer loci, defining a novel plasmid type within the IncH plasmid family. The blaNDM-1 gene was flanked by genetic elements that are distinct from those observed in other blaNDM-1-positive plasmids, including the groES and groEL chaperonin genes. This plasmid harboured the ESBL gene blaCTX-M-15 together with the quinolone resistance gene qnrB1. In addition, it harboured genes encoding resistance to tellurite, mercury, chloramphenicol and aminoglycosides. Interestingly, pNDM-MAR did not carry any 16S rRNA methylase gene, in contrast to other blaNDM-1-positive plasmids. Conclusions: This study underlines the diversity of genetic vehicles involved in the spread of the blaNDM-1 gene. Plasmid pNDM-MAR differed significantly from all known blaNDM-1-bearing plasmids. Comparative analysis of the pNDM-MAR sequence identified a novel type of IncH plasmid.
117 citations
TL;DR: This study describes two resistance regions localized on the bacterial chromosome of a clonal lineage of STM and monophasic STM that are widespread in Italy.
Abstract: Objectives: The aim of this study was to sequence the chromosomal region conferring resistance to ampicillin, streptomycin, sulphonamides and tetracycline (R-type ASSuT) in a Salmonella Typhimurium (STM) monophasic strain (4,[5],12:i:2) belonging to the PFGE profile STYMXB.0079. The presence of this resistance region and the analysis of its genetic environment was investigated in a selection of strains. Methods: A Sau3A1 genomic library was used to determine the nucleotide sequence of the genomic resistance region. PCRs were performed on 10 epidemiologically unrelated Salmonella strains, both STM and monophasic STM, with R-type ASSuT and PFGE profile STYMXB.0079, in order to investigate the presence of the resistance genes, the left and right junctions and the internal regions of the resistance region, as well as the genetic environment. Results: The genomic resistance region consisted of two regions, resistance region 1 (RR1), conferring resistance to ampicillin, streptomycin and sulphonamides, and resistance region 2 (RR2), conferring tetracycline resistance. These resistance regions were both surrounded by IS26 elements and sequence comparative analysis showed 99% sequence identity with a region of plasmid pO111_1 from an Escherichia coli strain. All 10 strains were positive for the four resistance genes, the left and right junctions and the internal regions of RR1 and RR2. Concerning the genetic environment, all the strains lacked the STM1053-1997 and STM2694 genes, while only monophasic STM strains showed deletion of the fljA-fljB operon. Conclusions: This study describes two resistance regions localized on the bacterial chromosome of a clonal lineage of STM and monophasic STM that are widespread in Italy.
61 citations