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Enterococcus sp. infection in pulmonary tissue
Scientific classification Edit this classification
Domain: Bacteria
Phylum: Bacillota
Class: Bacilli
Order: Lactobacillales
Family: Enterococcaceae
Genus: Enterococcus
(ex Thiercelin & Jouhaud 1903)
Schleifer & Kilpper-Bälz 1984

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.[4] 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.[4]

Physiology and classification[edit]

Enterococci are facultative anaerobic organisms, i.e., they are capable of cellular respiration in both oxygen-rich and oxygen-poor environments.[5] Though they are not capable of forming spores, enterococci are tolerant of a wide range of environmental conditions: extreme temperature (10–45 °C), pH (4.6–9.9), and high sodium chloride concentrations.[6]

Enterococci typically exhibit gamma-hemolysis on sheep's blood agar.[citation needed]


Members of the genus Enterococcus (from Greek έντερο, éntero, "intestine" and κοκκος, coccos, "granule") were classified as group D Streptococcus until 1984, when genomic DNA analysis indicated a separate genus classification would be appropriate.[7]


This genus appears to have evolved 425 million years ago to 500 million years ago.[8]


Important clinical infections caused by Enterococcus include urinary tract infections (see Enterococcus faecalis), bacteremia, bacterial endocarditis, diverticulitis, meningitis, and spontaneous bacterial peritonitis.[6][9][10] Sensitive strains of these bacteria can be treated with ampicillin, penicillin and vancomycin.[11] Urinary tract infections can be treated specifically with nitrofurantoin, even in cases of vancomycin resistance.[12]

Example of a workup algorithm of possible bacterial infection in cases with no specifically requested targets (non-bacteria, mycobacteria etc.), with most common situations and agents seen in a New England community hospital setting. Enterococcus is included near bottom-center.


Enterococcal meningitis is a rare complication of neurosurgery. It often requires treatment with intravenous or intrathecal vancomycin, yet it is debatable as to whether its use has any impact on outcome: the removal of any neurological devices is a crucial part of the management of these infections.[13] New epidemiological evidence has shown that enterococci are major infectious agent in chronic bacterial prostatitis.[14] Enterococci are able to form biofilm in the prostate gland, making their eradication difficult.[citation needed]

Antibacterial resistance[edit]

From a medical standpoint, an important feature of this genus is the high level of intrinsic antibiotic resistance. Some enterococci are intrinsically resistant to β-lactam-based antibiotics (penicillins, cephalosporins, carbapenems), as well as many aminoglycosides.[9] In the last two decades, particularly virulent strains of Enterococcus that are resistant to vancomycin (vancomycin-resistant Enterococcus, or VRE) have emerged in nosocomial infections of hospitalized patients, especially in the US.[6] Other developed countries, such as the UK, have been spared this epidemic, and, in 2005, Singapore managed to halt an epidemic of VRE.[15] Although quinupristin/dalfopristin (Synercid) was previously indicated for treatment of VRE in the USA, the FDA approval for this indication has since been retracted.[16] The rationale for the retraction of Synercid's indication for VRE was based upon poor efficacy in E. faecalis, which is implicated in the vast majority of VRE cases.[17][18] Tigecycline has also been shown to have antienterococcal activity, as has rifampicin.[19]

Water quality[edit]

In bodies of water, the acceptable level of contamination is very low; for example in the state of Hawaii, and most of the United States, the limit for water off its beaches is a five-week geometric mean of 35 colony-forming units per 100 ml of water, above which the state may post warnings to stay out of the ocean.[20] In 2004, measurement of enterococci took the place of fecal coliforms as the new USA federal standard for water quality at public saltwater beaches and alongside Escherichia coli at freshwater beaches.[21] It is believed to provide a higher correlation than fecal coliform with many of the human pathogens often found in city sewage.[22]


  1. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj ak al am an ao ap aq ar as at au av aw ax ay az ba bb bc bd be bf bg bh Parte, A.C. "Enterococcus". LPSN.
  2. ^ LPSN
  3. ^ LPSN entry for Enterococcus
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  14. ^ 38383-6
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  16. ^ Batts, D. H.; Lavin, B. S.; Eliopoulos, G. M. (2001). "Quinupristin/dalfopristin and linezolid: spectrum of activity and potential roles in therapy--a status report". Current Clinical Topics in Infectious Diseases. 21: 227–251. ISSN 0195-3842. PMID 11572153.
  17. ^ Collins, L A; Malanoski, G J; Eliopoulos, G M; Wennersten, C B; Ferraro, M J; Moellering, R C (March 1993). "In vitro activity of RP59500, an injectable streptogramin antibiotic, against vancomycin-resistant gram-positive organisms". Antimicrobial Agents and Chemotherapy. 37 (3): 598–601. doi:10.1128/aac.37.3.598. ISSN 0066-4804. PMC 187713. PMID 8460927.
  18. ^ Singh, Kavindra V.; Weinstock, George M.; Murray, Barbara E. (June 2002). "An Enterococcus faecalis ABC Homologue (Lsa) Is Required for the Resistance of This Species to Clindamycin and Quinupristin-Dalfopristin". Antimicrobial Agents and Chemotherapy. 46 (6): 1845–1850. doi:10.1128/AAC.46.6.1845-1850.2002. ISSN 0066-4804. PMC 127256. PMID 12019099.
  19. ^ 92784-8
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  21. ^ "Water Quality Standards for Coastal and Great Lakes Recreation Waters; Final Rule". Federal Register. 69 (220): 67218–67243. 16 November 2004. Retrieved 26 November 2014.
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