Characterization of virulence factors and clonal diversity of Enterococcus faecalis isolates from treated dental root canals.

The high prevalence of Enterococcus faecalis in root canal treated teeth with post-treatment disease, as evidenced by both molecular and traditional culturing methods, suggests that this species may be a key player in endodontic treatment failure. This study aimed to detect virulence factors by phenotypic and western blotting tests, and virulence genes by PCR from 20 clinical strains of E. faecalis isolated from treated root canals of teeth with (10) or without (10) apical periodontitis. Moreover, genomic diversity of these strains was assessed by pulsed-field gel electrophoresis (PFGE) and rep-PCR. All 20 strains presented the gelE gene (gelatinase), but 10 of them did not hydrolyze gelatin. Seven of the 10 gelatinase-producing isolates were recovered from root canals with lesions, which suggests a role for this virulence factor in the pathogenesis of post-treatment disease. The esp gene was expressed only in cases where gelatinase production was negative. The other virulence genes were found in 90% (efaA and ace genes), 45% (agg gene) and 95% (cpd gene) of the E. faecalis isolates. As for PFGE and rep-PCR, no specific clonal type of E. faecalis was found in association with teeth with or without disease, revealing the interindividual clonal diversity of endodontic infections.

Comparison of endodontic bacterial community structures in root-canal-treated teeth with or without apical periodontitis.

Bacterial occurrence in treated root canals, even in patients without post-treatment apical periodontitis, raises the possibility that factors other than mere bacterial presence can be determinants for a favourable outcome of endodontic treatment. Because these factors may be related to the bacterial communities colonizing the root canal, including virulence, density and interactions, the objective of this study was to compare the community structures found in root-canal-treated teeth with (12 samples) and without (11 samples) apical periodontitis lesions by means of a PCR-denaturing gradient gel electrophoresis fingerprinting approach. Results confirmed a polymicrobial composition even in treated patients without post-treatment disease. A large microbial community diversity was observed for treated teeth both with or without disease, but no specific pattern was detected for diseased teeth. Nevertheless, the number of bands from samples with apical periodontitis lesions was statistically significantly higher (P=0.04) than that from samples collected from root-canal-treated teeth without post-treatment apical periodontitis. Furthermore, predominant bands in samples from patients with apical disease were also observed.

Detection of Staphylococcus lugdunensis by a new species-specific PCR based on the fbl gene.

Staphylococcus lugdunensis are unusually virulent coagulase-negative staphylococci associated with skin infections and endocarditis. We developed an accurate and simple PCR assay to identify S. lugdunensis isolates based on detection of the fbl gene, which encodes a fibrinogen-binding protein involved in pathogen adhesion. The PCR assay was established using 16 reference strains of different Staphylococcus species and further validated with a collection of 63 clinical staphylococcal isolates that were also phenotypically characterized. Reliable results for the detection of S. lugdunensis isolates were obtained for 100% of the strains evaluated, indicating that this PCR assay can be used in the routine of microbiology laboratories as one more tool for correct species differentiation.