Virulence in Enterococci: chromosomal versus plasmidic location of virulence genes

Abstract number: 902_p962

Leitão Semedo T.M.


Enterococci are natural inhabitants of the gastrointestinal flora of humans and animals and are widely distributed in the environment. Members of this genus are recognised as important opportunistic pathogens responsible for serious infections but the molecular mechanisms of enterococcal virulence are not yet completely understood. In this study 42 Enterococci from different sources, including clinical isolates (from human and veterinarian origin), non-clinical isolates and reference strains from 19 enterococcal species, were typified and their virulence potential characterised. The relationships among these Enterococci were first analysed using SmaI pulsed-field gel electrophoresis and M13 PCR-fingerprinting, in order to evaluate the genomic heterogeneity of the isolates. Enterococci were also screened for several virulence traits such as cytolysin (cyl genes), adhesins (agg, esp, EfaAfs and EfaAfm genes) and gelatinase (gelE), revealing distinct virulence potentials. In Enterococcus faecalis, it was recently described that some virulence determinants can be clustered on large pathogenicity islands and not only in pheromone-responsive plasmids. Dot–blot DNA–DNA hybridisation was used to locate virulence determinants in the bacterial genome of the Enterococci under study. No conclusive results were obtained for esp and gelE, whereas EfaAfs and EfaAfm were found on the chromosome as expected. Although cyl genes and agg are plasmidic, in most isolates, they were detected on the chromosome of five strains, suggesting that these Enterococci may harbour a pathogenicity island. Beyond the widespread nature of virulence traits, chromosomal integration of virulence genes seems to occur in different enterococcal species and isolates from non-clinical sources.


Session Details

Date: 01/08/2007
Time: 00:00-00:00
Session name: XXIst ISTH Congress
Location: Oxford, UK
Presentation type:
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