Strain-Dependent Virulence Profiles in Enterococcus Faecalis Clinical Isolates

Objectives: Production of virulence factors is a critical pathogenicity trait that contributes to microbial invasion and degradation of host tissues. The opportunistic pathogen Enterococcus faecalis is involved in chronic and/or life-threatening infections of heart valves, peritoneum, urinary tract and dental root canals. The pathogenicity of E. faecalis is largely linked to its capacity to produce quorum sensing (QS)-regulated virulence factors such as cytolysin and extracellular gelatinase. The aim of this study was to characterize the QS-related genotype and phenotypic virulence profile in clinical isolates of E. faecalis.
Methods: E. faecalis strains (n=33) isolated from failed root canal treated teeth were screened for the presence of genes coding for cytolysin activator (cylA), E. faecalis system regulator (fsr ABC) and gelatinase (gelE) using colony-polymerase chain reaction (PCR). Cytolysin production and gelatinase activity were determined using defibrinated horse-blood and gelatine-supplemented Todd-Hewitt (THB) agar, respectively.
Results: The cylA gene and related cytolysin production were evident in 18% of the tested strains. Although 42.4 and 87.8% of the strains were positive for fsr ABC and gelE genes respectively, positive gelatinase phenotype was only displayed in the fsr⁺ gelE⁺ strains.
Conclusions: The presence of QS-regulated virulence traits in E. faecalis recovered from root canal environment suggests their potential role in the pathogenesis of persistent post-treatment infections.