Enterococcus faecalis, or E. faecalis, normally inhabit your gastrointestinal tract. However, as opportunistic pathogens, E. faecalis can cause serious problems. Laboratory studies suggest E. faecalis are fastidious, requiring very specific nutrients to grow. However, drug-resistant strains of E. faecalis can be difficult to kill. E. faecalis can grow in very harsh environments, including high heat and high salt, and can remain viable in non-nutritive environments for extended periods of time.
Minimum Nutritional Requirements
Enterococcus faecalis grow on different types of synthetic laboratory media. Two types of media typically used to culture E. faecalis include blood agar, plates containing blood cells from an animal, most commonly sheep, or chocolate agar, a medium similar to blood agar, but containing additional factors necessary for the growth of certain fastidious organisms. However, blood and chocolate agar plates, as well as the complex or semi-synthetic medium used for decades to grow these bacteria, do not consist of precisely defined nutrients. A 1993 "Journal of Bacteriology" article investigated the minimum nutrients required for E. faecalis growth. Researchers concluded that E. faecalis can grow on agar plates consisting of Davis Minimal Agar, a medium consisting of a precise combination of potassium phosphate, sodium citrate, magnesium sulfate and ammonium sulfate; six different B vitamins; calcium; and 20 essential amino acids. Interestingly, these studies confirmed that E. faecalis can grow in the absence of added purines and pyrimidines, the building blocks typically required for DNA synthesis.
Natural Nutritional Environment
The human body provides an ideal environment for E. faecalis growth. E. faecalis typically grows in the intestinal tract; in the female genital tract; and, less commonly, in the mouth. According to the Public Health Agency of Canada, E. faecalis accounts for 5 to 10 percent of all isolates from the human intestine. E. faecalis can also grow in household pets and livestock. Because the exact nutrients of these body parts vary from individual to individual, from species to species, and from one moment in time to another, the precise nutrients required for E. faecalis to survive in a body, under non-pathogenic conditions, cannot be exactly determined.
Inhibition of Growth
Antibiotics such as penicillin, ampicillin and vancomycincan prevent the growth of E. faecalis. However, drug-resistant strains of E. faecalis exist and pose a serious human health threat. According to the "Journal of Bacteriology," one of the most common organisms found in hospital-acquired infections occur as the result of Enteroccoccus acting as an opportunistic pathogen. Specifically, E. faecalis infections account for about 16 percent of all hospital-acquired urinary tract infections, according to the "Manual of Clinical Microbiology." Of the Enterococci isolated from infections, 85 to 95 percent consist of E. faecalis. Treatment for drug-resistant E. faecalis infections typically consists of a combination of an aminoglycoside such as gentamicin as well as a cell wall-active antibiotic, such as penicillin; the combination of which works synergistically to kill the bacteria. In addition, drug susceptibility screening before administration prevents the development of further drug-resistant strains.
Unique Growth Features
E. faecalis are very hardy. Although their optimal laboratory growing temperature is about 35 degrees C or 95 degrees F, they remain viable up to 80 degrees C or 176 degrees F. The Public Health Agency of Canada reports that E. faecalis can even remain viable on inanimate surfaces for up to four months. They can grow in soil, plants, water and food. They can also grow under conditions of very high salt.
References
- "Journal of Bacteriology"; Generation of Restriction Map of Enterococcus Faecalis OG1 and Investigation of Growth Requirements and Regions Encoding Biosynthetic Function; B.E. Murray, et al.; August 1993
- Missouri University of Science and Technology: Enterococcus Faecalis
- University of Maryland: Enterococcus Summary
- Centers for Disease Control and Prevention: Multiple-Drug Resistant Enterococci: The Nature of the Problem and an Agenda for the Future
- Public Health Agency of Canada: Enterococcus Faecalis Pathogen Data Safety Sheet
- Microbiology: The Osmoprotectant Glycine Betaine Inhibits Salt-Induced Cross-Tolerance Toward Lethal Treatment in Enterococcus Faecalis
