Enterococcus faecalis | |
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Scientific classification | |
Domain: | Bacteria |
Phylum: | Bacillota |
Class: | Bacilli |
Order: | Lactobacillales |
Family: | Enterococcaceae |
Genus: | Enterococcus |
Species: | E. faecalis |
Binomial name | |
Enterococcus faecalis (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, commensal bacterium inhabiting the gastrointestinal tracts of humans. [1] [2] Like other species in the genus Enterococcus , 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. [3] As an opportunistic pathogen, E. faecalis can cause life-threatening infections, especially in the nosocomial (hospital) environment, where the naturally high levels of antibiotic resistance found in E. faecalis contribute to its pathogenicity. [2] [ verification needed ]E. faecalis has been frequently found in reinfected, root canal-treated teeth in prevalence values ranging from 30% to 90% of the cases. [4] Re-infected root canal-treated teeth are about nine times more likely to harbor E. faecalis than cases of primary infections. [5]
E. faecalis is a nonmotile microbe; it ferments glucose without gas production, and does not produce a catalase reaction with hydrogen peroxide. 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. It catabolizes 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. [6]
E. faecalis is found in most healthy individuals, but can cause endocarditis and sepsis, urinary tract infections (UTIs), meningitis, and other infections in humans. [7] [8] 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. [9] [10] [11] A plasmid-encoded adhesin [12] called "aggregation substance" is also important for virulence in animal models of infection. [10] [13]
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, it cannot pass through the blood-brain barrier and be decarboxylated in the brain to become dopamine. [14]
E. faecalis is usually resistant to many commonly used antimicrobial agents (aminoglycosides, aztreonam and quinolones). [15] The resistance is mediated by the presence of multiple genes related to drug resistance in the chromosome or plasmid. [3]
Resistance to vancomycin in E. faecalis is becoming more common. [16] [17] Treatment options for vancomycin-resistant E. faecalis include nitrofurantoin (in the case of uncomplicated UTIs), [18] linezolid, quinupristin, tigecycline [15] and daptomycin, although ampicillin is preferred if the bacteria are susceptible. [19] Quinupristin/dalfopristin can be used to treat Enterococcus faecium but not E. faecalis. [19]
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. [20]
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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- and vancomycin-sensitive E. faecalis (lacking high-level resistance to aminoglycosides) strains can be treated by gentamicin and ampicillin antibiotics. A less nephrotoxic combination of ampicillin and ceftriaxone (even though E. faecalis is resistant to cephalosporins, ceftriaxone is working synergistically with ampicillin) may be used alternatively for ampicillin-susceptible E. faecalis. [21]
Daptomycin or linezolid may also show efficacy in case ampicillin and vancomycin resistance. [21]
A combination of penicillin and streptomycin therapy was used in the past. [21]
Tedizolid, telavancin, dalbavancin, and oritavancin antibiotics are FDA approved as treatments against EF. [15]
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 processes. [26] 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 of DNA double-strand breaks. [26]
The ability of E. faecalis to form biofilms contributes to its capacity to survive in extreme environments, and facilitates its involvement in persistent bacterial infection, particularly in the case of multi-drug resistant strains. [27] Biofilm formation in E. faecalis is associated with DNA release, and such release has emerged as a fundamental aspect of biofilm formation. [27] Conjugative plasmid DNA transfer in E. faecalis is enhanced by the release of peptide sex pheromones. [28]
Prior to 1984, enterococci were members of the genus Streptococcus ; thus, E. faecalis was known as Streptococcus faecalis. [29]
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. [30]
The E. faecalis genome consists of 3.22 million base pairs with 3,113 protein-coding genes. [31]
Glutamate racemase, hydroxymethylglutaryl-CoA synthase, diphosphomevalonate decarboxylase, topoisomerase DNA gyrase B, D-alanine—D-serine ligase, alanine racemase, phosphate acetyltransferase, NADH peroxidase,Phosphopantetheine adenylyltransferase (PPAT), acyl carrier protein, 3‐Dehydroquinate dehydratase and Deoxynucleotide triphosphate triphosphohydrolase are all potential molecules that may be used for treating EF infections. [15]
Bacillus haynesii CD223 and Advenella mimigardefordensis SM421 can inhibit the growth of Enterococcus faecalis. [32]
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. [33] Five of them have been shown to be involved in stress response and virulence. [34]
A genome-wide sRNA study suggested that some sRNAs are linked to the antibiotic resistance and stress response in another Enterococcus: E. faecium . [35]
Because E. faecalis is a common fecal bacterium in humans, recreational water facilities (such as swimming pools and beaches that allow visitors to swim in the ocean) often measure the concentrations of E. faecalis to assess the quality of their water. The higher the concentration, the worse the quality of the water. The practice of using E. faecalis as a quality indicator is recommended by the World Health Organization (WHO) as well as many developed countries after multiple studies have reported that higher concentrations of E. faecalis correlate to greater percentages of swimmer illness. This correlation exists in both freshwater and marine environments, so measuring E. faecalis concentrations to determine water quality applies to all recreational waters. However, the correlation does not imply that E. faecalis is the ultimate cause of swimmer illnesses. One alternative explanation is that higher levels of E. faecalis correspond to higher levels of human viruses, which cause sickness in swimmers. Although this claim may sound plausible, there is currently little evidence that establishes the link between E. faecalis and human virus (or other pathogens) levels. Thus, despite the strong correlation between E. faecalis and water quality, more research is needed to determine the causal relationship of this correlation. [36]
For recreational waters near or at beaches, E. faecalis can come from multiple sources, such as the sand and human bodies. Determining the sources of E. faecalis is crucial for controlling water contamination, though often the sources are non-point (for example, human bathers). As such, one study looked at how much E. faecalis is shed from bathers at the beach. The first group of participants immersed themselves in a large pool with marine water for 4 cycles of 15 minutes, both with and without contacting sand beforehand. The result shows a decrease in E. faecalis levels for each cycle, suggesting that people shed the most bacteria when they first get into a pool. The second group of participants entered small, individual pools after contact with beach sand, and researchers collected data on how much E. faecalis in the pool came from the sand brought by the participants and how much came from the participants’ shedding. The result shows that E. faecalis from the sand is very small compared to that from human shedding. Although this result may not apply to all sand types, a tentative conclusion is that human shedding is a major non-point source of E. faecalis in recreational waters. [37]
Staphylococcus aureus is a gram-positive spherically shaped bacterium, a member of the Bacillota, and is a usual member of the microbiota of the body, frequently found in the upper respiratory tract and on the skin. It is often positive for catalase and nitrate reduction and is a facultative anaerobe, meaning that it can grow without oxygen. Although S. aureus usually acts as a commensal of the human microbiota, it can also become an opportunistic pathogen, being a common cause of skin infections including abscesses, respiratory infections such as sinusitis, and food poisoning. Pathogenic strains often promote infections by producing virulence factors such as potent protein toxins, and the expression of a cell-surface protein that binds and inactivates antibodies. S. aureus is one of the leading pathogens for deaths associated with antimicrobial resistance and the emergence of antibiotic-resistant strains, such as methicillin-resistant S. aureus (MRSA). The bacterium is a worldwide problem in clinical medicine. Despite much research and development, no vaccine for S. aureus has been approved.
Vancomycin is a glycopeptide antibiotic medication used to treat certain bacterial infections. It is administered intravenously to treat complicated skin infections, bloodstream infections, endocarditis, bone and joint infections, and meningitis caused by methicillin-resistant Staphylococcus aureus. Blood levels may be measured to determine the correct dose. Vancomycin is also taken orally to treat Clostridioides difficile infections. When taken orally, it is poorly absorbed.
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 characteristics alone. Two species are common commensal organisms in the intestines of humans: E. faecalis (90–95%) and E. faecium (5–10%). Rare clusters of infections occur with other species, including E. casseliflavus, E. gallinarum, and E. raffinosus.
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, vancomycin-resistant enterococci (VRE), and methicillin-resistant Staphylococcus aureus (MRSA). The main uses are infections of the skin and pneumonia although it may be used for a variety of other infections including drug-resistant tuberculosis. It is used either by injection into a vein or by mouth.
Vancomycin-resistant Staphylococcus aureus (VRSA) are strains of Staphylococcus aureus that have acquired resistance to the glycopeptide antibiotic vancomycin. Bacteria can acquire resistance genes either by random mutation or through the transfer of DNA from one bacterium to another. Resistance genes interfere with the normal antibiotic function and allow bacteria to grow in the presence of the antibiotic. Resistance in VRSA is conferred by the plasmid-mediated vanA gene and operon. Although VRSA infections are uncommon, VRSA is often resistant to other types of antibiotics and a potential threat to public health because treatment options are limited. VRSA is resistant to many of the standard drugs used to treat S. aureus infections. Furthermore, resistance can be transferred from one bacterium to another.
Multiple drug resistance (MDR), multidrug resistance or multiresistance is antimicrobial resistance shown by a species of microorganism to at least one antimicrobial drug in three or more antimicrobial categories. Antimicrobial categories are classifications of antimicrobial agents based on their mode of action and specific to target organisms. The MDR types most threatening to public health are MDR bacteria that resist multiple antibiotics; other types include MDR viruses, parasites.
Staphylococcus haemolyticus is a member of the coagulase-negative staphylococci (CoNS). It is part of the skin flora of humans, and its largest populations are usually found at the axillae, perineum, and inguinal areas. S. haemolyticus also colonizes primates and domestic animals. It is a well-known opportunistic pathogen, and is the second-most frequently isolated CoNS. Infections can be localized or systemic, and are often associated with the insertion of medical devices. The highly antibiotic-resistant phenotype and ability to form biofilms make S. haemolyticus a difficult pathogen to treat. Its most closely related species is Staphylococcus borealis.
Vancomycin-resistant Enterococcus, or vancomycin-resistant enterococci (VRE), are bacterial strains of the genus Enterococcus that are resistant to the antibiotic vancomycin.
Acinetobacter baumannii is a typically short, almost round, rod-shaped (coccobacillus) Gram-negative bacterium. It is named after the bacteriologist Paul Baumann. It can be an opportunistic pathogen in humans, affecting people with compromised immune systems, and is becoming increasingly important as a hospital-derived (nosocomial) infection. While other species of the genus Acinetobacter are often found in soil samples, it is almost exclusively isolated from hospital environments. Although occasionally it has been found in environmental soil and water samples, its natural habitat is still not known.
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 vancomycin.
Enterococcus faecium is a Gram-positive, gamma-hemolytic or non-hemolytic bacterium in the genus Enterococcus. It can be commensal in the gastrointestinal tract of humans and animals, but it may also be pathogenic, causing diseases such as neonatal meningitis or endocarditis.
Ceftobiprole, sold under the brand name Zevtera among others, is a fifth-generation cephalosporin antibacterial used for the treatment of hospital-acquired pneumonia and community-acquired pneumonia. It is marketed by Basilea Pharmaceutica under the brand names Zevtera and Mabelio. Like other cephalosporins, ceftobiprole exerts its antibacterial activity by binding to important penicillin-binding proteins and inhibiting their transpeptidase activity which is essential for the synthesis of bacterial cell walls. Ceftobiprole has high affinity for penicillin-binding protein 2a of methicillin-resistant Staphylococcus aureus strains and retains its activity against strains that express divergent mecA gene homologues. Ceftobiprole also binds to penicillin-binding protein 2b in Streptococcus pneumoniae (penicillin-intermediate), to penicillin-binding protein 2x in Streptococcus pneumoniae (penicillin-resistant), and to penicillin-binding protein 5 in Enterococcus faecalis.
Enterococcus gallinarum is a species of Enterococcus. E. gallinarum demonstrates an inherent, low-level resistance to vancomycin. Resistance is due to a chromosomal gene, vanC, which encodes for a terminal D-alanine-D-serine instead of the usual D-alanine-D-alanine in cell wall peptidoglycan precursor proteins. That is a separate mechanism than the vancomycin resistance seen in VRE isolates of E. faecium and E. faecalis which is mediated by vanA or vanB. This species is known to cause clusters of infection, although it considered very rare. It is the only other known enterococcal species besides E. faecium and E. faecalis known to cause outbreaks and spread in hospitals.
Plasmid-mediated resistance is the transfer of antibiotic resistance genes which are carried on plasmids. Plasmids possess mechanisms that ensure their independent replication as well as those that regulate their replication number and guarantee stable inheritance during cell division. By the conjugation process, they can stimulate lateral transfer between bacteria from various genera and kingdoms. Numerous plasmids contain addiction-inducing systems that are typically based on toxin-antitoxin factors and capable of killing daughter cells that don't inherit the plasmid during cell division. Plasmids often carry multiple antibiotic resistance genes, contributing to the spread of multidrug-resistance (MDR). Antibiotic resistance mediated by MDR plasmids severely limits the treatment options for the infections caused by Gram-negative bacteria, especially family Enterobacteriaceae. The global spread of MDR plasmids has been enhanced by selective pressure from antimicrobial medications used in medical facilities and when raising animals for food.
Lancefield grouping is a system of classification that classifies catalase-negative Gram-positive cocci based on the carbohydrate composition of bacterial antigens found on their cell walls. The system, created by Rebecca Lancefield, was historically used to organize the various members of the family Streptococcaceae, which includes the genera Lactococcus and Streptococcus, but now is largely superfluous due to explosive growth in the number of streptococcal species identified since the 1970s. However, it has retained some clinical usefulness even after the taxonomic changes, and as of 2018, Lancefield designations are still often used to communicate medical microbiological test results.
Enterococcus malodoratus is a species of the genus Enterococcus and a gram positive bacteria capable of opportunistic pathogenic response. These microbes have a thick polypeptide layer. Enterococcus can be found in the gastrointestinal tracts of humans and other mammals. In a study on the enterococcal flora of swine, E. malodoratus was found in the intestines and feces. It was not identified within the tonsils of swine, nor within cats, calves, dogs, horse, or poultry. The name "malodoratus" translates to "ill smelling".
ESKAPE is an acronym comprising the scientific names of six highly virulent and antibiotic resistant bacterial pathogens including: Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp. The acronym is sometimes extended to ESKAPEE to include Escherichia coli. This group of Gram-positive and Gram-negative bacteria can evade or 'escape' commonly used antibiotics due to their increasing multi-drug resistance (MDR). As a result, throughout the world, they are the major cause of life-threatening nosocomial or hospital-acquired infections in immunocompromised and critically ill patients who are most at risk. P. aeruginosa and S. aureus are some of the most ubiquitous pathogens in biofilms found in healthcare. P. aeruginosa is a Gram-negative, rod-shaped bacterium, commonly found in the gut flora, soil, and water that can be spread directly or indirectly to patients in healthcare settings. The pathogen can also be spread in other locations through contamination, including surfaces, equipment, and hands. The opportunistic pathogen can cause hospitalized patients to have infections in the lungs, blood, urinary tract, and in other body regions after surgery. S. aureus is a Gram-positive, cocci-shaped bacterium, residing in the environment and on the skin and nose of many healthy individuals. The bacterium can cause skin and bone infections, pneumonia, and other types of potentially serious infections if it enters the body. S. aureus has also gained resistance to many antibiotic treatments, making healing difficult. Because of natural and unnatural selective pressures and factors, antibiotic resistance in bacteria usually emerges through genetic mutation or acquires antibiotic-resistant genes (ARGs) through horizontal gene transfer - a genetic exchange process by which antibiotic resistance can spread.
Kerry L. LaPlante is an American pharmacist, academic and researcher. She is the Dean at the University of Rhode Island College of Pharmacy. She is a Professor of Pharmacy and former department Chair of the Department of Pharmacy Practice at the University of Rhode Island, an adjunct professor of medicine at Brown University, an Infectious Diseases Pharmacotherapy Specialist, and the Director of the Rhode Island Infectious Diseases Fellowship and Research Programs at the Veterans Affairs Medical Center in Providence, Rhode Island.
Enterococcus casseliflavus is a species of commensal Gram-positive bacteria. Its name derived from the "flavus" the Latin word for yellow due to the bright yellow pigment that it produces. This organism can be found in the gastrointestinal tract of humans