Enterococcal surface protein Esp is important for biofilm formation of Enterococcus faecium E1162
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ABSTRACT: Enterococcus faecium and Enterococcus faecalis are commensal bacteria that colonize the gastrointestinal tract. Although these bacteria are in principal non-pathogenic, E. faecium and E. faecalis have emerged as important nosocomial pathogens with high-level resistance to antibiotics causing clinical infections including urinary tract infections, bacteremia and bacterial endocarditis in elderly and immunocompromised patients. Since the prevalence of enterococcal infections in hospitalized patients is still increasing every year, much research is focussed on the pathogenicity of these specific strains. Thus far, no clear evidence is has been found that explains the ecological success of these infectious causing strains. In order to understand what characteristics of E. faecium and E. faecalis really favour its ability to colonize and infect its host, this review focuses on the physiology of these bacteria rather then its pathology. The potential to degrade mucin glycoproteins via the production of specific glycosidases might contribute to an enhanced fitness of the organism because this substrate can be used as an additional nutrient source. Furthermore, E. faecium and E. faecalis have been shown to be resistant to bile acids. Besides bile salt hydrolases (BSH) that can detoxify conjugated bile acids (CBA), also other proteins, like gls24, are associated with CBA resistance. In addition to these characteristics, E. faecalis and to a lesser extend also E. faecium, are the primary source of Reactive Oxygen Species (ROS). In healthy individuals, the mucosa protects the underlying epithelial cell layer against harmful luminal contents like ROS. However, since E. faecium and E. faecalis produce glycosidases that reduce thickness of the mucosa, less protection is provided against ROS. ROS can cause genomic alterations, which is correlated to colorectal cancer. In conclusion, better understanding of the physiology of E. faecium and E. faecalis is essential to gain more insight into the pathogenicity of these bacteria. This review will discuss some essential adaptations of E. faecium and E. faecalis that might contribute to its increased fitness and prevalence.
Article: IS element IS16 as a molecular screening tool to identify hospital-associated strains of Enterococcus faecium.[show abstract] [hide abstract]
ABSTRACT: Hospital strains of Enterococcus faecium could be characterized and typed by various molecular methods (MLST, AFLP, MLVA) and allocated to a distinct clonal complex known as MLST CC17. However, these techniques are laborious, time-consuming and cost-intensive. Our aim was to identify hospital E. faecium strains and differentiate them from colonizing and animal variants by a simple, inexpensive and reliable PCR-based screening assay. We describe here performance and predictive value of a single PCR detecting the insertion element, IS16, to identify hospital E. faecium isolates within a collection of 260 strains of hospital, animal and human commensal origins. Specific primers were selected amplifying a 547-bp fragment of IS16. Presence of IS16 was determined by PCR screenings among the 260 E. faecium isolates. Distribution of IS16 was compared with a prevalence of commonly used markers for hospital strains, esp and hylEfm. All isolates were typed by MLST and partly by PFGE. Location of IS16 was analysed by Southern hybridization of plasmid and chromosomal DNA. IS16 was exclusively distributed only among 155 invasive strains belonging to the clonal complex of hospital-associated strains ("CC17"; 28 MLST types) and various vancomycin resistance genotypes (vanA/B/negative). The five invasive IS16-negative strains did not belong to the clonal complex of hospital-associated strains (CC17). IS16 was absent in all but three isolates from 100 livestock, food-associated and human commensal strains ("non-CC17"; 64 MLST types). The three IS16-positive human commensal isolates revealed MLST types belonging to the clonal complex of hospital-associated strains (CC17). The values predicting a hospital-associated strain ("CC17") deduced from presence and absence of IS16 was 100% and thus superior to screening for the presence of esp (66%) and/or hylEfm (46%). Southern hybridizations revealed chromosomal as well as plasmid localization of IS16. This simple screening assay for insertion element IS16 is capable of differentiating hospital-associated from human commensal, livestock- and food-associated E. faecium strains and thus allows predicting the epidemic strengths or supposed pathogenic potential of a given E. faecium isolate identified within the nosocomial setting.BMC Infectious Diseases 03/2011; 11:80. · 3.12 Impact Factor
Article: Intra- and interspecies genomic transfer of the Enterococcus faecalis pathogenicity island.[show abstract] [hide abstract]
ABSTRACT: Enterococci are the third leading cause of hospital associated infections and have gained increased importance due to their fast adaptation to the clinical environment by acquisition of antibiotic resistance and pathogenicity traits. Enterococcus faecalis harbours a pathogenicity island (PAI) of 153 kb containing several virulence factors including the enterococcal surface protein (esp). Until now only internal fragments of the PAI or larger chromosomal regions containing it have been transferred. Here we demonstrate precise excision, circularization and horizontal transfer of the entire PAI element from the chromosome of E. faecalis strain UW3114. This PAI (ca. 200 kb) contained some deletions and insertions as compared to the PAI of the reference strain MMH594, transferred precisely and integrated site-specifically into the chromosome of E. faecalis (intergenic region) and Enterococcus faecium (tRNAlys). The internal PAI structure was maintained after transfer. We assessed phenotypic changes accompanying acquisition of the PAI and expression of some of its determinants. The esp gene is expressed on the surface of donor and both transconjugants. Biofilm formation and cytolytic activity were enhanced in E. faecalis transconjugants after acquisition of the PAI. No differences in pathogenicity of E. faecalis were detected using a mouse bacteraemia and a mouse peritonitis models (tail vein and intraperitoneal injection). A 66 kb conjugative pheromone-responsive plasmid encoding erm(B) (pLG2) that was transferred in parallel with the PAI was sequenced. pLG2 is a pheromone responsive plasmid that probably promotes the PAI horizontal transfer, encodes antibiotic resistance features and contains complete replication and conjugation modules of enterococcal origin in a mosaic-like composition. The E. faecalis PAI can undergo precise intra- and interspecies transfer probably with the help of conjugative elements like conjugative resistance plasmids, supporting the role of horizontal gene transfer and antibiotic selective pressure in the successful establishment of certain enterococci as nosocomial pathogens.PLoS ONE 01/2011; 6(4):e16720. · 4.09 Impact Factor
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