Vancomycin-Resistant Enterococcus
Encyclopedia
Vancomycin-resistant Enterococcus, or vancomycin-resistant enterococci (VRE), are bacterial strains of the genus Enterococcus
that are resistant
to the antibiotic
vancomycin
. To become VRE, vancomycin-sensitive enterococci typically obtain new DNA in the form of plasmids or transposons which encode genes
that confer vancomycin resistance. This acquired vancomycin resistance is distinguished from the lower-level, natural vancomycin resistance of certain enterococcal species including E. gallinarum
and E. casseliflavus.
High-level vancomycin-resistant E. faecalis
and E. faecium
clinical isolates were first documented in Europe in the late 1980s. Since then, VRE have been associated with outbreaks of hospital-acquired (nosocomial
) infections around the world. In the United States, vancomycin-resistant E. faecium
was associated with 4% of healthcare-associated infections reported to the Centers for Disease Control and Prevention
National Healthcare Safety Network from January 2006 to October 2007.
VRE can be carried by healthy people who have come into contact with the bacteria. The most likely place where such contact can occur is in a hospital (nosocomial infection), although it is thought that a significant percentage of intensively-farmed chicken
also carry VRE.
, Van-B VRE is resistant to vancomycin but sensitive to teicoplanin, and Van-C is only partly resistant to vancomycin, and sensitive to teicoplanin. In the US, linezolid
is commonly used to treat VRE, as teicoplanin is not available.
The mechanism of resistance to vancomycin found in enterococcus involves the alteration to the terminal amino acid residues of the NAM/NAG-peptide subunits, under normal conditions, D-alanyl-D-alanine, to which vancomycin binds. The D-alanyl-D-lactate variation results in the loss of one hydrogen-bonding interaction (four, as opposed to five for D-alanyl-D-alanine) being possible between vancomycin and the peptide. This loss of just one point of interaction results in a 1000-fold decrease in affinity. The D-alanyl-D-serine variation causes a six-fold loss of affinity between vancomycin and the peptide, likely due to steric hindrance.
Some VREs respond to the presence of vancomycin rather than just its effect on the cell wall.
use is a risk factor for colonization and infection by VRE, and restriction of cephalosporin usage has been associated with decreased VRE infection and transmission in hospitals.
In 2005, Lactobacillus rhamnosus GG (LGG), a strain of L. rhamnosus
, was used successfully for the first time to treat gastrointestinal carriage of VRE in renal patients.
Enterococcus
Enterococcus is a genus of lactic acid bacteria of the phylum Firmicutes. Enterococci are Gram-positive cocci that often occur in pairs or short chains, and are difficult to distinguish from streptococci on physical characteristics alone. Two species are common commensal organisms in the...
that are resistant
Antibiotic resistance
Antibiotic resistance is a type of drug resistance where a microorganism is able to survive exposure to an antibiotic. While a spontaneous or induced genetic mutation in bacteria may confer resistance to antimicrobial drugs, genes that confer resistance can be transferred between bacteria in a...
to the antibiotic
Antibiotic
An antibacterial is a compound or substance that kills or slows down the growth of bacteria.The term is often used synonymously with the term antibiotic; today, however, with increased knowledge of the causative agents of various infectious diseases, antibiotic has come to denote a broader range of...
vancomycin
Vancomycin
Vancomycin INN is a glycopeptide antibiotic used in the prophylaxis and treatment of infections caused by Gram-positive bacteria. It has traditionally been reserved as a drug of "last resort", used only after treatment with other antibiotics had failed, although the emergence of...
. To become VRE, vancomycin-sensitive enterococci typically obtain new DNA in the form of plasmids or transposons which encode genes
Gênes
Gênes is the name of a département of the First French Empire in present Italy, named after the city of Genoa. It was formed in 1805, when Napoleon Bonaparte occupied the Republic of Genoa. Its capital was Genoa, and it was divided in the arrondissements of Genoa, Bobbio, Novi Ligure, Tortona and...
that confer vancomycin resistance. This acquired vancomycin resistance is distinguished from the lower-level, natural vancomycin resistance of certain enterococcal species including E. gallinarum
Enterococcus gallinarum
Enterococcus gallinarum is a species of Enterococcus.E. gallinarum demonstrates an inherent, low-level resistance to vancomycin....
and E. casseliflavus.
High-level vancomycin-resistant E. faecalis
Enterococcus faecalis
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. It is among the main constituents of some probiotic food supplements. Like other species in the genus...
and E. faecium
Enterococcus faecium
Enterococcus faecium is a Gram-positive, alpha hemolytic or nonhemolytic bacterium in the genus Enterococcus. It can be commensal in the human intestine, but it may also be pathogenic, causing diseases such as neonatal meningitis.Vancomycin-resistant E. faecium is often referred to as VRE.Some...
clinical isolates were first documented in Europe in the late 1980s. Since then, VRE have been associated with outbreaks of hospital-acquired (nosocomial
Nosocomial infection
A nosocomial infection , also known as a hospital-acquired infection or HAI, is an infection whose development is favoured by a hospital environment, such as one acquired by a patient during a hospital visit or one developing among hospital staff...
) infections around the world. In the United States, vancomycin-resistant E. faecium
Enterococcus faecium
Enterococcus faecium is a Gram-positive, alpha hemolytic or nonhemolytic bacterium in the genus Enterococcus. It can be commensal in the human intestine, but it may also be pathogenic, causing diseases such as neonatal meningitis.Vancomycin-resistant E. faecium is often referred to as VRE.Some...
was associated with 4% of healthcare-associated infections reported to the Centers for Disease Control and Prevention
Centers for Disease Control and Prevention
The Centers for Disease Control and Prevention are a United States federal agency under the Department of Health and Human Services headquartered in Druid Hills, unincorporated DeKalb County, Georgia, in Greater Atlanta...
National Healthcare Safety Network from January 2006 to October 2007.
VRE can be carried by healthy people who have come into contact with the bacteria. The most likely place where such contact can occur is in a hospital (nosocomial infection), although it is thought that a significant percentage of intensively-farmed chicken
Industrial agriculture (animals)
Industrial animal agriculture or industrial livestock production is a modern form of intensive farming that refers to the industrialized production of livestock, including cattle, poultry and fish...
also carry VRE.
Mechanism of acquired vancomycin resistance
Six different types of vancomycin resistance are shown by enterococcus : Van-A, Van-B, Van-C, Van-D, Van-E and Van-F. Of these, only Van-A, Van-B and Van-C have been seen in general clinical practice, so far. The significance is that Van-A VRE is resistant to both vancomycin and teicoplaninTeicoplanin
Teicoplanin is an antibiotic used in the prophylaxis and treatment of serious infections caused by Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus and Enterococcus faecalis. It is a glycopeptide antibiotic extracted from Actinoplanes teichomyceticus, with a similar...
, Van-B VRE is resistant to vancomycin but sensitive to teicoplanin, and Van-C is only partly resistant to vancomycin, and sensitive to teicoplanin. In the US, linezolid
Linezolid
Linezolid is a synthetic antibiotic used for the treatment of serious infections caused by Gram-positive bacteria that are resistant to several other antibiotics...
is commonly used to treat VRE, as teicoplanin is not available.
The mechanism of resistance to vancomycin found in enterococcus involves the alteration to the terminal amino acid residues of the NAM/NAG-peptide subunits, under normal conditions, D-alanyl-D-alanine, to which vancomycin binds. The D-alanyl-D-lactate variation results in the loss of one hydrogen-bonding interaction (four, as opposed to five for D-alanyl-D-alanine) being possible between vancomycin and the peptide. This loss of just one point of interaction results in a 1000-fold decrease in affinity. The D-alanyl-D-serine variation causes a six-fold loss of affinity between vancomycin and the peptide, likely due to steric hindrance.
Some VREs respond to the presence of vancomycin rather than just its effect on the cell wall.
Prevention and treatment of VRE infection
CephalosporinCephalosporin
The cephalosporins are a class of β-lactam antibiotics originally derived from Acremonium, which was previously known as "Cephalosporium".Together with cephamycins they constitute a subgroup of β-lactam antibiotics called cephems.-Medical use:...
use is a risk factor for colonization and infection by VRE, and restriction of cephalosporin usage has been associated with decreased VRE infection and transmission in hospitals.
In 2005, Lactobacillus rhamnosus GG (LGG), a strain of L. rhamnosus
Lactobacillus rhamnosus
Lactobacillus rhamnosus is a bacterium that was originally considered to be a subspecies of L. casei, but later genetic research found it to be a species of its own. Some strains of L. rhamnosus are being used as probiotics. The species is sometimes used in yogurt and other dairy products. Some...
, was used successfully for the first time to treat gastrointestinal carriage of VRE in renal patients.
See also
- Methicillin-resistant Staphylococcus aureusMethicillin-resistant Staphylococcus aureusMethicillin-resistant Staphylococcus aureus is a bacterium responsible for several difficult-to-treat infections in humans. It is also called multidrug-resistant Staphylococcus aureus and oxacillin-resistant Staphylococcus aureus...
(MRSA) - MDR-TB
- XDR-TB
- Drug resistanceDrug resistanceDrug resistance is the reduction in effectiveness of a drug such as an antimicrobial or an antineoplastic in curing a disease or condition. When the drug is not intended to kill or inhibit a pathogen, then the term is equivalent to dosage failure or drug tolerance. More commonly, the term is used...
- Antibiotic resistanceAntibiotic resistanceAntibiotic resistance is a type of drug resistance where a microorganism is able to survive exposure to an antibiotic. While a spontaneous or induced genetic mutation in bacteria may confer resistance to antimicrobial drugs, genes that confer resistance can be transferred between bacteria in a...