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Identification of resistance and virulence factors in an epidemic Enterobacter hormaechei outbreak strain

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Author: Paauw, A. · Caspers, M.P.M. · Leverstein-van Hall, M.A. · Schuren, F.H.J. · Montijn, R.C. · Verhoef, J. · Fluit, A.C.
Type:article
Date:2009
Institution: TNO Kwaliteit van Leven
Source:Microbiology, 5, 155, 1478-1488
Identifier: 241686
doi: doi:10.1099/mic.0.024828-0
Keywords: Biology · Biotechnology · Bacterial DNA · Outer membrane protein · Virulence factor · Bacterial strain · Bacterial virulence · Bacterium isolate · DNA fragmentation · Enterobacter cloacae · Enterobacter hormaechei · Epidemic · Genetic marker · Genetic resistance · Nonhuman · Pathogenicity island · Plasticity · Salmonella enterica · Enterobacteriaceae infection · Genetics · Isolation and purification · Metabolism · Microbiology · Bacteria (microorganisms) · Salmonella enterica · Bacterial Proteins · Disease Outbreaks · Enterobacter · Enterobacteriaceae Infections · Netherlands · Plasmids · Virulence Factors

Abstract

Bacterial strains differ in their ability to cause hospital outbreaks. Using comparative genomic hybridization, Enterobacter cloacae complex isolates were studied to identify genetic markers specific for Enterobacter cloacae complex outbreak strains. No outbreak-specific genes were found that were common in all investigated outbreak strains. Therefore, the aim of our study was to identify specific genetic markers for an Enterobacter hormaechei outbreak strain (EHOS) that caused a nationwide outbreak in The Netherlands. Most EHOS isolates carried a large conjugative plasmid (pQC) containing genes encoding heavy-metal resistance, mobile elements, pili-associated proteins and exported proteins as well as multiple-resistance genes. Furthermore, the chromosomally encoded high-pathogenicity island (HPI) was highly associated with the EHOS strain. In addition, other DNA fragments were identified that were associated with virulence: three DNA fragments known to be located on a virulence plasmid (pLVPK), as well as phage- and plasmid-related sequences. Also, four DNA fragments encoding putative pili with the most homology to pili of Salmonella enterica were associated with the EHOS. Finally, four DNA fragments encoding putative outer-membrane proteins were negatively associated with the EHOS. In conclusion, resistance and putative virulence genes were identified in the EHOS that may have contributed to increased epidemicity. The high number of genes detected in the EHOS that were related to transferable elements reflects the genomic plasticity of the E. cloacae complex and may explain the emergence of the EHOS in the hospital environment. © 2009 SGM.