Abstract
BackgroundThe Gram-positive bacterium Enterococcus faecium is an important cause of nosocomial infections in immunocompromized patients.ResultsWe present a pyrosequencing-based comparative genome analysis of seven E. faecium strains that were isolated from various sources. In the genomes of clinical isolates several antibiotic resistance genes were identified, including the vanA transposon that confers resistance to vancomycin in two strains. A functional comparison between E. faecium and the related opportunistic pathogen E. faecalis based on differences in the presence of protein families, revealed divergence in plant carbohydrate metabolic pathways and oxidative stress defense mechanisms. The E. faecium pan-genome was estimated to be essentially unlimited in size, indicating that E. faecium can efficiently acquire and incorporate exogenous DNA in its gene pool. One of the most prominent sources of genomic diversity consists of bacteriophages that have integrated in the genome. The CRISPR-Cas system, which contributes to immunity against bacteriophage infection in prokaryotes, is not present in the sequenced strains. Three sequenced isolates carry the esp gene, which is involved in urinary tract infections and biofilm formation. The esp gene is located on a large pathogenicity island (PAI), which is between 64 and 104 kb in size. Conjugation experiments showed that the entire esp PAI can be transferred horizontally and inserts in a site-specific manner.ConclusionsGenes involved in environmental persistence, colonization and virulence can easily be aquired by E. faecium. This will make the development of successful treatment strategies targeted against this organism a challenge for years to come.
Highlights
The Gram-positive bacterium Enterococcus faecium is an important cause of nosocomial infections in immunocompromized patients
E1071 was isolated from a patient not suffering from an enterococcal infection and subsequent typing of the isolate showed that it was different from the strain causing the outbreak
We found that the isolates originating from the hospital have acquired multiple antibiotic resistance genes and, in addition, have genes that may play a role in the colonization and infection of hospitalized patients
Summary
The Gram-positive bacterium Enterococcus faecium is an important cause of nosocomial infections in immunocompromized patients. The two most studied enterococcal species are E. faecium and E. faecalis, which are genetically distinct as shown by their 16S rRNA sequences and the sequences of the housekeeping gene atpA [2]. Both E. faecium and E. faecalis are an Several studies have shown that the E. faecium strains that cause infections in hospitalized patients are different from the strains that colonize the gastro-intestinal tract of the healthy human host [11,12,13]. Insertion sequence (IS) elements were the most prominent group of genes enriched in CC17 but, in addition, genes with a proven or proposed role in E. faecium virulence were identified in CC17 isolates [11]
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