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''Enterococcus faecalis'' – formerly classified as part of the group D ''
Streptococcus ''Streptococcus'' is a genus of gram-positive ' (plural ) or spherical bacteria that belongs to the family Streptococcaceae, within the order Lactobacillales (lactic acid bacteria), in the phylum Bacillota. Cell division in streptococci occurs ...
'' system – is a
Gram-positive In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall. Gram-positive bacte ...
,
commensal Commensalism is a long-term biological interaction (symbiosis) in which members of one species gain benefits while those of the other species neither benefit nor are harmed. This is in contrast with mutualism, in which both organisms benefit fro ...
bacterium Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...
inhabiting the
gastrointestinal tract The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organ (biology), organs of the digestive syste ...
s of humans. Like other species in the
genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
''
Enterococcus ''Enterococcus'' is a large genus of lactic acid bacteria of the phylum Bacillota. Enterococci are gram-positive cocci that often occur in pairs (diplococci) or short chains, and are difficult to distinguish from streptococci on physical char ...
'', ''E. faecalis'' is found in healthy humans and can be used as a probiotic. The probiotic strains such as Symbioflor1 and EF-2001 are characterized by the lack of specific genes related to drug resistance and pathogenesis. As an opportunistic pathogen, ''E. faecalis'' can cause life-threatening infections, especially in the
nosocomial A hospital-acquired infection, also known as a nosocomial infection (from the Greek , meaning "hospital"), is an infection that is acquired in a hospital or other health care facility. To emphasize both hospital and nonhospital settings, it is ...
(hospital) environment, where the naturally high levels of
antibiotic resistance Antimicrobial resistance (AMR) occurs when microbes evolve mechanisms that protect them from the effects of antimicrobials. All classes of microbes can evolve resistance. Fungi evolve antifungal resistance. Viruses evolve antiviral resistance. ...
found in ''E. faecalis'' contribute to its pathogenicity. ''E. faecalis'' has been frequently found in reinfected, 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.


Physiology

''E. faecalis'' is a nonmotile microbe; it ferments
glucose Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, u ...
without gas production, and does not produce a catalase reaction with
hydrogen peroxide Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscous than water. It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3% ...
. It produces a reduction of
litmus milk Litmus milk is a milk-based medium used to distinguish between different species of bacteria. The lactose (milk sugar), litmus (pH indicator), and casein (milk protein) contained within the medium can all be metabolized by different types of bacter ...
, but does not liquefy gelatin. It shows consistent growth throughout nutrient broth which is consistent with being a facultative anaerobe. It catabolizes a variety of energy sources, including
glycerol Glycerol (), also called glycerine in British English and glycerin in American English, is a simple triol compound. It is a colorless, odorless, viscous liquid that is sweet-tasting and non-toxic. The glycerol backbone is found in lipids known ...
, lactate,
malate Malic acid is an organic compound with the molecular formula . It is a dicarboxylic acid that is made by all living organisms, contributes to the sour taste of fruits, and is used as a food additive. Malic acid has two stereoisomeric forms (L ...
,
citrate Citric acid is an organic compound with the chemical formula HOC(CO2H)(CH2CO2H)2. It is a colorless weak organic acid. It occurs naturally in citrus fruits. In biochemistry, it is an intermediate in the citric acid cycle, which occurs in the ...
, arginine,
agmatine Agmatine, also known as 4-aminobutyl-guanidine, is an aminoguanidine that was discovered in 1910 by Albrecht Kossel. Agmatine is a chemical substance which is naturally created from the amino acid arginine. Agmatine has been shown to exert modula ...
, and many
keto acids Keto may refer to: * The Ket people (also known as Кето), an ethnic group of the Siberian North * Ceto or Keto, a sea goddess in Greek mythology * Ketone or keto group, the functional group in the chemical compounds ketones * Ketoconazole, a m ...
. Enterococci survive very harsh environments, including extremely alkaline pH (9.6) and salt concentrations. They resist
bile salt Bile acids are steroid acids found predominantly in the bile of mammals and other vertebrates. Diverse bile acids are synthesized in the liver. Bile acids are conjugated with taurine or glycine residues to give anions called bile salts. P ...
s, detergents, heavy metals,
ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an Alcohol (chemistry), alcohol with the chemical formula . Its formula can be also written as or (an ethyl ...
, azide, and
desiccation Desiccation () is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic (attracts and holds water) substance that induces or sustains such a state in its local vicinity in a moderately sealed container. ...
. They can grow in the range of 10 to 45 °C and survive at temperatures of 60 °C for 30 min.


Pathogenesis

''E. faecalis'' is found in most healthy individuals, but can cause
endocarditis Endocarditis is an inflammation of the inner layer of the heart, the endocardium. It usually involves the heart valves. Other structures that may be involved include the interventricular septum, the chordae tendineae, the mural endocardium, or the ...
and
sepsis Sepsis, formerly known as septicemia (septicaemia in British English) or blood poisoning, is a life-threatening condition that arises when the body's response to infection causes injury to its own tissues and organs. This initial stage is follo ...
,
urinary tract infection A urinary tract infection (UTI) is an infection that affects part of the urinary tract. When it affects the lower urinary tract it is known as a bladder infection (cystitis) and when it affects the upper urinary tract it is known as a kidney ...
s (UTIs),
meningitis Meningitis is acute or chronic inflammation of the protective membranes covering the brain and spinal cord, collectively called the meninges. The most common symptoms are fever, headache, and neck stiffness. Other symptoms include confusion or ...
, and other infections in humans. Several virulence factors are thought to contribute to ''E. faecalis'' infections. A
plasmid A plasmid is a small, extrachromosomal DNA molecule within a cell that is physically separated from chromosomal DNA and can replicate independently. They are most commonly found as small circular, double-stranded DNA molecules in bacteria; how ...
-encoded
hemolysin Hemolysins or haemolysins are lipids and proteins that cause lysis of red blood cells by disrupting the cell membrane. Although the lytic activity of some microbe-derived hemolysins on red blood cells may be of great importance for nutrient acqu ...
, called the
cytolysin Cytolysin refers to the substance secreted by microorganisms, plants or animals that is specifically toxic to individual cells, in many cases causing their dissolution through lysis. Cytolysins that have a specific action for certain cells are n ...
, 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 A plasmid is a small, extrachromosomal DNA molecule within a cell that is physically separated from chromosomal DNA and can replicate independently. They are most commonly found as small circular, double-stranded DNA molecules in bacteria; how ...
-encoded adhesin called "aggregation substance" is also important for virulence in animal models of infection. ''E. faecalis'' contains a tyrosine decarboxylase enzyme capable of decarboxylating L-dopa, a crucial drug in the treatment of Parkinson's disease. If L-dopa is decarboxylated in the
gut microbiome Gut microbiota, gut microbiome, or gut flora, are the microorganisms, including bacteria, archaea, fungi, and viruses that live in the digestive tracts of animals. The gastrointestinal metagenome is the aggregate of all the genomes of the gut ...
, it cannot pass through the blood-brain barrier and be decarboxylated in the brain to become dopamine.


Antibacterial resistance


Multi drug resistance

''E. faecalis'' is usually resistant to many commonly used
antimicrobial An antimicrobial is an agent that kills microorganisms or stops their growth. Antimicrobial medicines can be grouped according to the microorganisms they act primarily against. For example, antibiotics are used against bacteria, and antifungals ar ...
agents (
aminoglycosides Aminoglycoside is a medicinal and bacteriologic category of traditional Gram-negative antibacterial medications that inhibit protein synthesis and contain as a portion of the molecule an amino-modified glycoside ( sugar). The term can also refer ...
,
aztreonam Aztreonam, sold under the brand name Azactam among others, is an antibiotic used primarily to treat infections caused by gram-negative bacteria such as ''Pseudomonas aeruginosa''. This may include bone infections, endometritis, intra abdominal ...
and
quinolones Quinolone may refer to: * 2-Quinolone * 4-Quinolone 4-Quinolone is an organic compound derived from quinoline. It and 2-quinolone are the two most important parent (meaning simplified) quinolones. 4-Quinolone exists in equilibrium with a mino ...
. The resistance is mediated by the presence of multiple genes related to drug resistance in the chromosome or plasmid. Resistance to
vancomycin Vancomycin is a glycopeptide antibiotic medication used to treat a number of bacterial infections. It is recommended intravenously as a treatment for complicated skin infections, bloodstream infections, endocarditis, bone and joint infections, ...
in ''E. faecalis'' is becoming more common. Treatment options for vancomycin-resistant ''E. faecalis'' include
nitrofurantoin Nitrofurantoin is an antibacterial medication used to treat urinary tract infections, but it is not as effective for kidney infections. It is taken by mouth. Common side effects include nausea, loss of appetite, diarrhea, and headaches. Rarely ...
(in the case of uncomplicated UTIs),
linezolid Linezolid is an antibiotic used for the treatment of infections caused by Gram-positive bacteria that are resistant to other antibiotics. Linezolid is active against most Gram-positive bacteria that cause disease, including streptococci, v ...
,
quinupristin {{Drugbox , IUPAC_name = ''N''-{(6''R'',9''S'',10''R'',13''S'',15a''S'',18''R'',22''S'',24a''S'')-18- { 3''S'')-1-azabicyclo .2.2.html"_;"title="3''S'')-1-azabicyclo[2.2.2">3''S'')-1-azabicyclo[2.2.2ct-3-ylthioethyl}-22-[4-_...
,_tigecycline.html" ;"title=".2.2ct-3-ylthio">.2.2.html" ;"title="3''S'')-1-azabicyclo[2.2.2">3''S'')-1-azabicyclo[2.2.2ct-3-ylthioethyl}-22-[4- ...
, tigecycline">.2.2ct-3-ylthio">.2.2.html" ;"title="3''S'')-1-azabicyclo[2.2.2">3''S'')-1-azabicyclo[2.2.2ct-3-ylthioethyl}-22-[4- ...
, tigecycline and daptomycin, although
ampicillin Ampicillin is an antibiotic used to prevent and treat a number of bacterial infections, such as respiratory tract infections, urinary tract infections, meningitis, salmonellosis, and endocarditis. It may also be used to prevent group B stre ...
is preferred if the bacteria are susceptible. Quinupristin/dalfopristin can be used to treat ''Enterococcus faecium'' but not ''E. faecalis''. In root-canal treatments,
NaOCl Sodium hypochlorite (commonly known in a dilute solution as bleach) is an inorganic chemical compound with the formula NaOCl (or NaClO), comprising a sodium cation () and a hypochlorite anion (or ). It may also be viewed as the sodium salt o ...
and
chlorhexidine Chlorhexidine (CHX) (commonly known by the salt forms chlorhexidine gluconate and chlorhexidine digluconate (CHG) or chlorhexidine acetate) is a disinfectant and antiseptic that is used for skin disinfection before surgery and to sterilize surgi ...
(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''.


Development of antibiotic resistance


Combined drug therapies

According to one study combined drug therapy has shown some efficacy in cases of severe infections (e.g. heart valves infections) against susceptible strains of ''E. faecalis''.
Ampicillin Ampicillin is an antibiotic used to prevent and treat a number of bacterial infections, such as respiratory tract infections, urinary tract infections, meningitis, salmonellosis, and endocarditis. It may also be used to prevent group B stre ...
- and
vancomycin Vancomycin is a glycopeptide antibiotic medication used to treat a number of bacterial infections. It is recommended intravenously as a treatment for complicated skin infections, bloodstream infections, endocarditis, bone and joint infections, ...
-sensitive '' E. faecalis'' (lacking high-level resistance to
aminoglycoside Aminoglycoside is a medicinal and bacteriologic category of traditional Gram-negative antibacterial medications that inhibit protein synthesis and contain as a portion of the molecule an amino-modified glycoside (sugar). The term can also refer ...
s) strains can be treated by gentamicin and
ampicillin Ampicillin is an antibiotic used to prevent and treat a number of bacterial infections, such as respiratory tract infections, urinary tract infections, meningitis, salmonellosis, and endocarditis. It may also be used to prevent group B stre ...
antibiotics. A less
nephrotoxic Nephrotoxicity is toxicity in the kidneys. It is a poisonous effect of some substances, both toxic chemicals and medications, on kidney function. There are various forms, and some drugs may affect kidney function in more than one way. Nephrotoxins ...
combination of ampicillin and
ceftriaxone Ceftriaxone, sold under the brand name Rocephin, is a third-generation cephalosporin antibiotic used for the treatment of a number of bacterial infections. These include middle ear infections, endocarditis, meningitis, pneumonia, bone and joint ...
(even though ''E. faecalis'' is resistant to cephalosporins,
ceftriaxone Ceftriaxone, sold under the brand name Rocephin, is a third-generation cephalosporin antibiotic used for the treatment of a number of bacterial infections. These include middle ear infections, endocarditis, meningitis, pneumonia, bone and joint ...
is working synergistically with ampicillin) may be used alternatively for ampicillin-susceptible ''E. faecalis''.
Daptomycin Daptomycin, sold under the brand name Cubicin among others, is a lipopeptide antibiotic used in the treatment of systemic and life-threatening infections caused by Gram-positive organisms. Daptomycin was removed from the World Health Organiza ...
or
linezolid Linezolid is an antibiotic used for the treatment of infections caused by Gram-positive bacteria that are resistant to other antibiotics. Linezolid is active against most Gram-positive bacteria that cause disease, including streptococci, v ...
may also show efficacy in case ampicillin and vancomycin resistance. A combination of
penicillin Penicillins (P, PCN or PEN) are a group of β-lactam antibiotics originally obtained from ''Penicillium'' moulds, principally '' P. chrysogenum'' and '' P. rubens''. Most penicillins in clinical use are synthesised by P. chrysogenum using ...
and
streptomycin Streptomycin is an antibiotic medication used to treat a number of bacterial infections, including tuberculosis, ''Mycobacterium avium'' complex, endocarditis, brucellosis, ''Burkholderia'' infection, plague, tularemia, and rat bite fever. F ...
therapy was used in the past.
Tedizolid Tedizolid (formerly torezolid, trade name Sivextro), is an oxazolidinone-class antibiotic. Tedizolid phosphate is a phosphate ester prodrug of the active compound tedizolid. It was developed by Cubist Pharmaceuticals, following acquisition of ...
,
telavancin Telavancin (trade name Vibativ) is a bactericidal lipoglycopeptide for use in MRSA or other Gram-positive infections. Telavancin is a semi-synthetic derivative of vancomycin. The FDA approved the drug in September 2009 for complicated skin and ...
,
dalbavancin Dalbavancin, sold under the brand names Dalvance in the US and Xydalba in the EU among others, is a second-generation lipoglycopeptide antibiotic medication. It belongs to the same class as vancomycin, the most widely used and one of the treatm ...
, and
oritavancin Oritavancin, sold under the brand name Orbactiv among others, is a semisynthetic glycopeptide antibiotic medication for the treatment of serious Gram-positive bacterial infections. Its chemical structure as a lipoglycopeptide is similar to vanc ...
antibiotics are FDA approved as treatments against EF.


Survival and virulence factors

* Endures prolonged periods of nutritional deprivation * Binds to dentin and proficiently spreads into dentinal tubules via chain propagation * Alters host responses * Suppresses the action of lymphocytes * Possesses lytic enzymes, cytolysin, aggregation substance,
pheromone A pheromone () is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to affect the behavio ...
s, and
lipoteichoic acid Lipoteichoic acid (LTA) is a major constituent of the cell wall of gram-positive bacteria. These organisms have an inner (or cytoplasmic) membrane and, external to it, a thick (up to 80 nanometer) peptidoglycan layer. The structure of LTA varies ...
* Utilizes serum as a nutritional source * Produces extracellular superoxide under selected growth conditions that can generate chromosomal instability in mammalian cells * Resists intracanal medicaments (e.g. calcium hydroxide), although a study proposes elimination from root canals after using a mixture of a tetracycline isomer, an acid, and a detergent ** Maintains pH homeostasis ** Properties of dentin lessen the effect of calcium hydroxide * Competes with other cells * Forms a
biofilm A biofilm comprises any syntrophic consortium of microorganisms in which cells stick to each other and often also to a surface. These adherent cells become embedded within a slimy extracellular matrix that is composed of extracellular ...
* Activates the host protease plasminogen in a fashion that increases local tissue destruction


DNA repair

In human blood, ''E. faecalis'' is subjected to conditions that damage its DNA, but this damage can be tolerated by the use of
DNA repair DNA repair is a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. In human cells, both normal metabolic activities and environmental factors such as radiation can cause DNA dam ...
processes.Ha KP, Clarke RS, Kim GL, Brittan JL, Rowley JE, Mavridou DAI, Parker D, Clarke TB, Nobbs AH, Edwards AM. Staphylococcal DNA Repair Is Required for Infection. mBio. 2020 Nov 17;11(6):e02288-20. doi: 10.1128/mBio.02288-20. PMID: 33203752; PMCID: PMC7683395 This damage tolerance depends, in part, on the two protein complex RexAB, encoded by the ''E. faecalis'' genome, that is employed in the
recombinational repair Homologous recombination is a type of genetic recombination in which genetic information is exchanged between two similar or identical molecules of double-stranded or single-stranded nucleic acids (usually DNA as in cellular organisms but may be ...
of DNA double-strand breaks.


Historical

Prior to 1984, enterococci were members of the genus ''
Streptococcus ''Streptococcus'' is a genus of gram-positive ' (plural ) or spherical bacteria that belongs to the family Streptococcaceae, within the order Lactobacillales (lactic acid bacteria), in the phylum Bacillota. Cell division in streptococci occurs ...
''; 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.


Genome structure

The ''E. faecalis'' genome consists of 3.22 million base pairs with 3,113 protein-coding genes.


Treatment research

Glutamate racemase In enzymology, glutamate racemase (MurI with a capital ''i'') () is an enzyme that catalysis, catalyzes the chemical reaction :L-glutamate \rightleftharpoons D-glutamate Hence, this enzyme RacE has one substrate (biochemistry), substrate, glutam ...
,
hydroxymethylglutaryl-CoA synthase In molecular biology, hydroxymethylglutaryl-CoA synthase or HMG-CoA synthase is an enzyme which catalyzes the reaction in which acetyl-CoA condenses with acetoacetyl-CoA to form 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA). This reaction compris ...
,
diphosphomevalonate decarboxylase Diphosphomevalonate decarboxylase (), most commonly referred to in scientific literature as mevalonate diphosphate decarboxylase, is an enzyme that catalysis, catalyzes the chemical reaction :ATP + (R)-5-diphosphomevalonate \rightleftharpoons A ...
, topoisomerase
DNA gyrase DNA gyrase, or simply gyrase, is an enzyme within the class of topoisomerase and is a subclass of Type II topoisomerases that reduces topological strain in an ATP dependent manner while double-stranded DNA is being unwound by elongating RNA-poly ...
B,
D-alanine—D-serine ligase D-Alanine—D-serine ligase (, ''VanC'', ''VanE'', ''VanG'') is an enzyme with List of enzymes, systematic name ''D-alanine:D-serine ligase (ADP-forming)''. This enzyme catalysis, catalyses the following chemical reaction : D-alanine + D-serine + ...
,
alanine racemase In enzymology, an alanine racemase () is an enzyme that catalyzes the chemical reaction :L-alanine \rightleftharpoons D-alanine Hence, this enzyme has one substrate, L-alanine, and one product, D-alanine. This enzyme belongs to the family o ...
,
phosphate acetyltransferase In enzymology, a phosphate acetyltransferase () is an enzyme that catalyzes the chemical reaction :acetyl-CoA + phosphate \rightleftharpoons CoA + acetyl phosphate The substrates of this enzyme are acetyl-CoA and phosphate, whereas its two pro ...
,
NADH peroxidase In enzymology, a NADH peroxidase () is an enzyme that catalyzes the chemical reaction :NADH + H+ + H2O2 \rightleftharpoons NAD+ + 2 H2O The presumed function of NADH peroxidase is to inactivate H2O2 generated within the cell, for example by gl ...
,Phosphopantetheine adenylyltransferase (PPAT),
acyl carrier protein The acyl carrier protein (ACP) is a cofactor of both fatty acid and polyketide Polyketides are a class of natural products derived from a precursor molecule consisting of a chain of alternating ketone (or reduced forms of a ketone) and methylene ...
, 3‐Dehydroquinate dehydratase and Deoxynucleotide triphosphate triphosphohydrolase are all potential molecules that may be used for treating EF infections.


Small RNA

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''.


See also

*
Anti-Q RNA Anti-Q RNA (formerly Qa RNA) is a small ncRNA from the conjugal plasmid pCF10 of ''Enterococcus faecalis''. It is coded in cis to its regulatory target, prgQ, but can also act in trans Trans- is a Latin prefix meaning "across", "beyond", or "on ...


References


External links


Type strain of ''Enterococcus faecalis'' at Bac''Dive'' – the Bacterial Diversity Metadatabase
{{Taxonbar, from=Q140014 faecalis Bacteria described in 1906