Enterococcus faecalis
| Enterococcus faecalis | |
|---|---|
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| Scientific classification | |
| Domain: | Bacteria |
| Kingdom: | Eubacteria |
| Phylum: | Firmicutes |
| Class: | Bacilli |
| Order: | Lactobacillales |
| Family: | Enterococcaceae |
| Genus: | Enterococcus |
| Species: | faecalis |
| Binomial name | |
| Enterococcus faecalis |
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Enterococcus faecalis – formerly classified as part of the Group D Streptococcus system – is a Gram-positive, commensal bacterium inhabiting the gastrointestinal tracts of humans and other mammals.[1] Like other species in the genus Enterococcus, E. faecalis 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.[1] E. faecalis has been frequently found in root canal-treated teeth in prevalence values ranging from 30% to 90% of the cases.[2] Root canal-treated teeth are about nine times more likely to harbor E. faecalis than cases of primary infections.[3]
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Physiology[edit]
E. faecalis is a nonmotile, facultatively anaerobic microbe; it ferments glucose 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. Growth on nutrient broth is consistent with being facultatively anaerobic.They catabolize a variety of energy sources including carbohydrates, glycerol, lactate,malate, citrate, arginine, agmatine, and many � keto acids . Enterococci survive very harsh environments including extreme 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 a temperature of 60°C for 30 min.[stuart et al. 2006]
Pathogenesis[edit]
E. faecalis can cause endocarditis and bacteremia, urinary tract infections (UTI), meningitis, and other infections in humans.[4][5] 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.[6][7][8] A plasmid-encoded factor called "aggregation substance" is also important for virulence in animal models of infection.[7][9]
Antibacterial resistance[edit]
E. faecalis is resistant to many commonly used antimicrobial agents (aminoglycosides, aztreonam, cephalosporins, clindamycin, the semisynthetic penicillins nafcillin and oxacillin, and trimethoprim-sulfamethoxazole).[citation needed] Resistance to vancomycin in E. faecalis is becoming more common.[10][11] Treatment options for vancomycin-resistant E. faecalis include linezolid and daptomycin, although ampicillin is preferred if the bacteria are susceptible.[12] Quinupristin/dalfopristin can be used to treat Enterococcus faecium but not E. faecalis.[12]
Survival and Virulence Factors[edit]
- Endures prolonged periods of nutritional deprivation
- Binds to dentin and proficiently invades dentinal tubules
- Alters host responses
- Suppresses the action of lymphocytes
- Possesses lytic enzymes, cytolysin, aggregation substance,pheromones, and lipoteichoic acid
- Utilizes serum as a nutritional source
- Resists intracanal medicaments (i.e. Ca(OH)2)
- Maintains pH homeostasis
- Properties of dentin lessen the effect of calcium hydroxide
- Competes with other cells
- Forms a biofilm
[Review Article Stuart et al. JOE 2006]
Historical[edit]
Prior to 1984, enterococci were members of the genus Streptococcus: thus E. faecalis was known as Streptococcus faecalis.[13]
See also[edit]
References[edit]
- ^ a b Ryan KJ, Ray CG (editors) (2004). Sherris Medical Microbiology (4th ed.). McGraw Hill. pp. 294––5. ISBN 0-8385-8529-9.
- ^ Molander A, Reit C, Dahlen G, Kvist T: Microbiological status of root-filled teeth with apical periodontitis, Int Endod J 31:1, 1998
- ^ Rocas, IN, Siquiera JF, Jr., Santos KR: Association of Enterococcus faecalis with different forms of periradicular diseases, J Endod 30:315, 2004.
- ^ Murray, BE. (Jan 1990). "The life and times of the Enterococcus.". Clin Microbiol Rev 3 (1): 46–65. PMID 2404568.
- ^ 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. PMID 18947320.
- ^ Huycke, MM.; Spiegel, CA.; Gilmore, MS. (Aug 1991). "Bacteremia caused by hemolytic, high-level gentamicin-resistant Enterococcus faecalis.". Antimicrob Agents Chemother 35 (8): 1626–34. PMID 1929336.
- ^ a b Chow, JW.; Thal, LA.; Perri, MB.; Vazquez, JA.; Donabedian, SM.; Clewell, DB.; Zervos, MJ. (Nov 1993). "Plasmid-associated hemolysin and aggregation substance production contribute to virulence in experimental enterococcal endocarditis.". Antimicrob Agents Chemother 37 (11): 2474–7. PMID 8285637.
- ^ Ike, Y.; Hashimoto, H.; Clewell, DB. (Aug 1984). "Hemolysin of Streptococcus faecalis subspecies zymogenes contributes to virulence in mice.". Infect Immun 45 (2): 528–30. PMID 6086531.
- ^ Hirt, H.; Schlievert, PM.; Dunny, GM. (Feb 2002). "In vivo induction of virulence and antibiotic resistance transfer in Enterococcus faecalis mediated by the sex pheromone-sensing system of pCF10.". Infect Immun 70 (2): 716–23. PMID 11796604.
- ^ Amyes SG (May 2007). "Enterococci and streptococci". Int. J. Antimicrob. Agents. 29 Suppl 3: S43–52. doi:10.1016/S0924-8579(07)72177-5. PMID 17659211.
- ^ Courvalin P (January 2006). "Vancomycin resistance in gram-positive cocci". Clin. Infect. Dis. 42 Suppl 1: S25–34. doi:10.1086/491711. PMID 16323116.
- ^ a b Arias, CA.; Contreras, GA.; Murray, BE. (Jun 2010). "Management of multidrug-resistant enterococcal infections.". Clin Microbiol Infect 16 (6): 555–62. doi:10.1111/j.1469-0691.2010.03214.x. PMID 20569266.
- ^ 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. Sys. Bacteriol. 34: 31–34. doi:10.1099/00207713-34-1-31.
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