(Andrewes and Horder, 1906) Schleifer and Kilpper-Bälz, 1984
Enterococcus faecalis – formerly classified as part of the group D Streptococcus system – is a Gram-positive, commensalbacterium inhabiting the gastrointestinal tracts of humans and other mammals. Like other species in the genusEnterococcus, E. faecalis is found in healthy humans, but can cause life-threatening infections in humans, especially in the nosocomial (hospital) environment, where the naturally high levels of antibiotic resistance found in E. faecalis contribute to its pathogenicity.E. faecalis has been frequently found in re-infected root canal-treated teeth in prevalence values ranging from 30% to 90% of the cases. Re-infected root canal-treated teeth are about nine times more likely to harbor E. faecalis than cases of primary infections.
E. faecalis is a nonmotile microbe; it fermentsglucose without gas production, and does not produce a catalase reaction with hydrogen peroxide. It can produce a pseudocatalase reaction if grown on blood agar. The reaction is usually weak. It produces a reduction of litmus milk, but does not liquefy gelatin. It shows consistent growth throughout nutrient broth which is consistent with being a facultative anaerobe. They catabolize a variety of energy sources including glycerol, lactate, malate, citrate, arginine, agmatine, and many keto acids. Enterococci survive very harsh environments including extremely alkaline pH (9.6) and salt concentrations. They resist bile salts, detergents, heavy metals, ethanol, azide, and desiccation. They can grow in the range of 10 to 45 °C and survive at temperatures of 60 °C for 30 min.
E. faecalis is found in most healthy individuals, but can cause endocarditis and septicemia, urinary tract infections, meningitis, and other infections in humans. Several virulence factors are thought to contribute to E. faecalis infections. A plasmid-encoded hemolysin, called the cytolysin, is important for pathogenesis in animal models of infection, and the cytolysin in combination with high-level gentamicin resistance is associated with a five-fold increase in risk of death in human bacteremia patients. A plasmid-encoded adhesin called "aggregation substance" is also important for virulence in animal models of infection.
This is a Gram stain for Enterococcus faecalis under 1000 magnification (bright field microscopy)
In root canal treatments, NaOCl and chlorhexidine (CHX) are used to fight E. faecalis before isolating the canal. However, recent studies determined that NaOCl or CHX showed low ability to eliminate E. faecalis.
Survival and virulence factors
Endures prolonged periods of nutritional deprivation
Binds to dentin and proficiently invades dentinal tubules
Prior to 1984, enterococci were members of the genus Streptococcus; thus, E. faecalis was known as Streptococcus faecalis.
In 2013, a combination of cold denaturation and NMR spectroscopy was used to show detailed insights into the unfolding of the E. faecalis homodimeric repressor protein CylR2.
The E. faecalis genome consists of 3.22 million base pairs with 3,113 protein-coding genes.
Bacterial small RNAs play important roles in many cellular processes. 11 small RNAs have been experimentally characterised in E. faecalis V583 and detected in various growth phases. Five of them have been shown to be involved in stress response and virulence.
A genome-wide sRNA study suggested that some sRNAs are linked to the antibiotic resistance and stress response in another Enteroccocus: E. faecium.
^Rocas, I.; Siqueira, J.; Santos, K. (2004). "Association of Enterococcus faecalis With Different Forms of Periradicular Diseases". Journal of Endodontics. 30 (5): 315–320. doi:10.1097/00004770-200405000-00004.
^ abStuart, C. H.; Schwartz, S. A.; Beeson, T. J.; Owatz, C. B. (2006). "Enterococcus faecalis: Its role in root canal treatment failure and current concepts in retreatment". Journal of endodontics. 32 (2): 93–8. doi:10.1016/j.joen.2005.10.049. PMID16427453.
^Hidron AI, Edwards JR, Patel J, et al. (November 2008). "NHSN annual update: antimicrobial-resistant pathogens associated with healthcare-associated infections: annual summary of data reported to the National Healthcare Safety Network at the Centers for Disease Control and Prevention, 2006-2007". Infect Control Hosp Epidemiol. 29 (11): 996–1011. doi:10.1086/591861. PMID18947320.
^Schleifer KH, Kilpper-Balz R (1984). "Transfer of Streptococcus faecalis and Streptococcus faecium to the genus Enterococcus nom. rev. as Enterococcus faecalis comb. nov. and Enterococcus faecium comb. nov". Int. J. Syst. Bacteriol. 34: 31–34. doi:10.1099/00207713-34-1-31.