Relationship of Biofilm Formation and gelE Gene Expression in Enterococcus faecalis Recovered from Root Canals in Patients Requiring Endodontic Retreatment

Introduction: Enterococcus faecalis is known to be the most frequently detected species in root canals with failed endodontic treatment. Many studies are available on biofilm formation and the expression of virulence factors such as gelatinase (gelE) in E. faecalis. However, the relationship of biofilm formation and the expression of gelE in E. faecalis recovered from root canals undergoing orthograde retreatment is not well understood. Methods: E. faecalis was isolated from clinical samples of root canal retreatment, and the expression of gelE in E. faecalis was assessed. Automatic microplate reader and scanning electron microscopy were used to investigate the biofilm formation ability of IF. faecalis isolates. Real-time quantitative polymerase chain reaction was used for detecting the expression of gelE in biofilm-positive and biofilm-negative E. faecalis isolates. Results: The detection rate of E.;Faecalis in the root canal retreatment cases was 39.26%. An automatic microplate reader showed that most isolates were able to form biofilms, and the biofilm formation ability of strains isolated from the teeth without a sinus tract was better than that with a sinus tract (P < .05). The expression of gelE was stronger in the cases of apical radiolucency than in those without the symptom (P < .05). The expression of gelE was higher in the biofilm-positive than in biofilm-negative strains (P < .05). Conclusions: Biofilm formation in E. faecalis was facilitated in the cases without a sinus tract. In the cases of apical radiolucency and in the biofilm-positive strains, the expression of gelE was higher. (J Endod 2011;37:631-636)