In some cases, this bacterium can also be found in the mouth or vaginal tract.
In healthy people, or when present in normal amounts, Enterococcus does not usually cause a problem.
But if it spreads to other areas of the body, it may cause life-threatening infections. People in hospital settings or who have underlying health conditions are at a higher risk of developing an infection.
While there are 17 or more species of Enterococcus, only two are commonly found in humans: E. faecalis and E. faecium.
This article focuses on E. faecalis, its associated infections, how it is transmitted, and treatment options.
What is Enterococcus faecalis?
Enterococcus faecalis bacteria. Originally, this bacteria was associated with the Streptococcus.
Image credit: Janice Haney Carr, CDC/Pete Wardell.
Until 1984, E. faecalis was known as Streptococcus faecalis. Scientists previously categorized the bacteria as part of the genus Streptococcus.
According to the Centers for Disease Control and Prevention (CDC), E. faecalis is responsible for approximately 80 percent of cases of human infection.
The bacteria can cause infection in people when it enters wounds, blood, or urine. People with weakened immune systems are particularly at risk, such as those who:
- have weak immunity due to disease or surgery
- are undergoing cancer treatment
- are on dialysis
- are receiving an organ transplant
- have HIV or AIDS
- have had a root canal
People in hospital settings are particularly vulnerable to E. faecalis infection because hospitalized patients tend to have reduced immunity. The common use of intravascular and urinary catheter devices can also contribute to the spread of infection, as these instruments frequently harbor the E. faecalis bacteria.
E. faecalis is believed to be one of the top three leading causes of hospital-acquired infection.
A urinary tract infection can be caused by E. faecalis, and an infection by this type of bacteria can make urination painful.
E. faecalis contributes to a number of infections in people, some of which can be life-threatening.
The bacteria may cause:
- bacteremia, the presence of bacteria in the blood
- abdominal and pelvic infections
- urinary tract infections
- oral infections, particularly with root canals
- septicemia, or blood poisoning
- wound infections
- endocarditis, an infection of the lining of the heart
- enterococcal meningitis, an uncommon form of meningitis
Symptoms of E. faecalis infection depend on the location of the infection. They can include:
- painful urination
- stomach cramping
E. faecalis has both natural and acquired immunity from antibiotic treatment. As a result, it is one of the most antibiotic-resistant types of bacteria.
The bacteria can also tolerate a variety of conditions. It can survive in a range of temperatures and acidic or alkaline environments.
E. faecalis can resist many antibiotic treatments due to:
- Biofilm formation: The bacteria can bind together to form a thin but sturdy layer, known as a biofilm, which can stick firmly to a surface.
- Nutritional needs: E. faecalis can endure long periods of time without a nutritional source. It can even use the serum in the blood as a source of nutrition.
- Penicillin-binding proteins (PBPs): These proteins make E. faecalis naturally resistant to penicillin. Penicillin inhibits E. faecalis activity but it does not destroy the bacterial cells.
- Environmental folic acid absorption: Bacteria require folic acid to grow. Most cannot absorb it from the environment so must make their own. Medications that interfere with the production of folic acid can often destroy bacterial infections. However, E. faecalis can absorb folic acid from the environment, so these medications have little effect.
Transmission and prevention
Enterococci are most commonly transmitted due to poor hygiene.
Since it is naturally present in the gastrointestinal tract, E. faecalis is found in fecal matter. Improper cleaning of items containing fecal matter, or not washing hands after restroom use, can increase the risk of bacterial transmission.
Everyday objects such as telephones, doorknobs, towels, and soaps can also contain E. faecalis.
The bacteria can spread throughout hospitals if healthcare workers do not wash their hands between patients. If not thoroughly cleaned, catheters or dialysis ports can also transmit infection.
Practicing good hygiene, especially in a hospital setting, can help prevent the spread of E. faecalis infection.
Preventive measures include:
- thoroughly washing hands, including the fingertips and thumbs, after using the restroom
- washing hands before eating or drinking
- ensuring that healthcare professionals wash their hands before contact with IV lines, catheters, and dressings
- ensuring that medical professionals thoroughly clean their hands between patients
- avoiding the use of other people's personal hygiene items, such as soaps, washcloths, towels, and razors
- avoiding sitting on the beds of other patients
- avoiding the toilets of other patients as well as toilets that look dirty or soiled
- regular cleaning of restrooms and toilets
- wiping down doorknobs, remote controls, telephones, and other commonly shared objects
- frequent hand washing by hospital patients, staff, and visitors
Antibiotics are usually prescribed to treat uncomplicated infections. Different types of antibiotics are prescribed, depending on how serious the infection is.
Due to its drug-resistant mechanisms, Enterococcus infection poses a significant treatment challenge to healthcare professionals.
Before treatment, healthcare providers often take samples of the bacteria from patients. They profile the sample's susceptibility to various types of treatment including ampicillin, penicillin, and vancomycin.
An uncomplicated infection can often be treated with a single antibiotic. If there's no antibiotic resistance, ampicillin is the preferred medication.
Other drug options include:
- ampicillin with sulbactam
More severe infections can include sepsis, endocarditis, or meningitis. These infections may need to be treated with a combination of a cell wall-active agent and a class of antibiotics known as aminoglycosides.
Cell wall-active agents are antibiotics that target the bacterial cell wall, inhibiting cell growth. Examples include ampicillin, vancomycin, and aminoglycosides, which include gentamicin and streptomycin.
For a more serious infection, treatment can last several weeks.
Enterococcal infections commonly occur in people who are already ill. This can make it difficult to determine if the bacterial infection is responsible for any subsequent illness or death.
Some research suggests that the outlook for people with E. faecalis infection is linked to their health status, not the presence of bacterial strains.
Other studies have found that patients with an infection caused by strains of vancomycin-resistant Enterococcus had a higher mortality rate than those with strains susceptible to the antibiotic.
Infections caused by antibiotic-resistant bacteria tend to result in longer hospital stays, higher health care costs, and higher mortality rates when compared with infections from antibiotic-susceptible bacteria.
Good hygiene practices are the best way to prevent the transmission of E. faecalis infection.