Enterococcus faecalis
Classification
Higher order taxa
Bacteria; Firmicutes; Bacilli; Lactobacillales; Enterococcaceae; Enterococcus
Genus
Enterococcus faecalis
Description and significance
Enterococcus are gram-positive cocci that can survive harsh conditions in nature. They can be found in soil, water, and plants. Some strains are used for the manufacture of foods whereas others are the cause of serious human and animal infections (i.e. they are known to colonize the gastrointestinal and gential tracts of humans). They are associated with both community and hospitial acquired infections. Enterocci can grow at a temperature range of 10 to 42°C and in environments with broad pH values. Some are known to be motile.While there are over 15 species of the Enterococcus genus, 80-90% of clinical isolates are E. faecalis. Enterocci typically form short chains or are arranged in pairs. However, under certain growth conditions, they elongate and appear coocobacillary. In general, enterococci are alpha-hemlytic. Some possess the group D Lancefield antigen and can be detected using monoclonal antibody-based agglutination tests. Enterococci are typically catalase negative, and are anaerobic. They are able to grow in 6.5% NaCl, can hydrolyze esculin in the presence of 40% bile salts and are pyrrolidonyl arylamidase and leucine arylamidase positive. Enterococci have proven to present a therapeutic challenge because of their resistance to many antimicrobial drugs, including cell-wall active agents, aminoglycosides, penicillin and ampicillin, and vancomycin. In the last decade, vancomycin-resistnat enerococci have become a major challenge. The enterococci have the capacity to acquire a wide variety if antimicrobial resistance factors which present serious problems in the management of patients with enteroccoal infections. In general, entercoccal isolates with lowered susceptibility to vancomycin can be categorized as vanA, vanB, and vanC. vanA and vanB pose the greatest threat because they are the most resistant and the resistance genes are carried on a plasmid. Since the resistance genes are carried on a plasmid they readily transferable. E. faecalis strains are categorized as vanA isolates. E. faecalis are also resistant to teicoplanin. Enterococcal strains that are vancomycin dependent have been reported, but are rare and are less common that vancomycin-resistant strains.
Genome structure
E. faecalis contains five plasmids. One plasmid, pAM373, is a 36.7 kb conjugative plasmid that encodes a response to a peptide sex pheromone, cAM373. While there are many unique features of this plasmid, the structure of the plasmid is similar to other known pheromone-responsive plasmids such as pAD1, pCF10 and pPD1. Similarities include the pheromone-binding surface protein (TraC) and a negatively regulating protein (TraA), but there is an absence of a determinant equivalent to traB in pAD1 and a determinant for surface-exclusion protein. The precursor structure of the inhibitor peptide iAM373 was identified, and its determinant (iam373) was found to be about 500 nt upstream of a transcription terminator t1.
The strain chosen for genome DNA sequencing was E. faecalis V583, the frist vancomycin-resistant isolate in the United States. The genome of strain V583 was sequenced by The Institute for Genome Research (TIGR).
Cell structure and metabolism
Describe any interesting features and/or cell structures; how it gains energy; what important molecules it produces.
Ecology
Describe any interactions with other organisms (included eukaryotes), contributions to the environment, effect on environment, etc.
Pathology
Enterococci have emerged in the last part of the 20th century as a major cause of nosocomial infections, and within this group Enterococcus faecalis causes the majority of human enterococcal infections. These infections may be local or systematic and include uninary tract and abdominal infections, wound infections, bacteremia, and endocarditis. Enterococci are part of the many taxa that make up the normal human intestinal flora and are capable of surviving numerous environmental challenges such as temperature extremes and the presence of bile salts. Their acquisition of resistance to multiple antibiotics has made these bacteria a major health problem. The National Nosocomial Infection Surveillance (NNIS) system has reported a rapid rise in the incidence of infection and colonization with vancomycin-resistant enterococci (VRE) since 1989. This poses serious health problems, which include the lack of available antimicrobial therapy for VRE infections, because most VRE strains harbor resistance to multiple antibiotics (e.g. aminoglyscoides and ampicillin) and vancomycin is often the antibiotic of last resort.
How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.
Application to Biotechnology
Does this organism produce any useful compounds or enzymes? What are they and how are they used?
Current Research
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References
De la Maza, Luis M., Marie T. Pezzlo, and Janet T. Shigei. Color Atlas of Medical Bacteriology. Washington, DC: American Society for Microbiology, 2004.
Edited by Richard A. Martinez of UC San Diego, student of Rachel Larsen.
