Virulence factors of Enterococcus faecalis in relation to pulp diseases and periapical infections

Enterococci are Gram-positive, catalase-negative, facultative anaerobic bacteria. They inhabit the oral cavity and gastrointestinal tract in humans as normal commensals. However, they can also cause infections of the urinary tract, surgical wound infections, neonatal sepsis and endocarditis. Enterococcus faecalis is associated with great number of refractory endodontic infections. The prevalence of these bacteria ranges from 24 to 77% in teeth with failed endodontic treatment and E. faecalis very often coexists with chronic apical periodontitis. Understanding the virulence, ecology and epidemiology of E. faecalis is essential for limiting all kinds of diseases caused by this pathogen. This article focuses on the bacterial mechanisms related to endodontic infections and periradicular inflammatory response. The most explored virulence factors are: the aggregation substance, surface adhesins, lytic enzymes, lipoteicholic acid, sex pheromones. All of them are associated with specific stages of tissue invasion. E. faecalis has also developed elaborated mechanisms of antibiotic resistance, as well as the ability to organize in a biofilm and overcome low-nutrient conditions. These adaptations help in the modulation of host immune response and make E. faecalis very difficult to eradicate by available antibiotics and disinfectants. Recognition and understanding of the nature of this pathogen will help endodontic microbiology to completely eliminate endodontic infections for successful endodontic treatment.