Enterococcus

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Enterococcus
Enterococcus histological pneumonia 01.png
Enterococcus sp. infection in pulmonary tissue
Scientific classification
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Enterococcus

(ex Thiercelin & Jouhaud 1903)
Schleifer & Kilpper-Bälz 1984
Species[1]

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Enterococcus is a large genus of lactic acid bacteria of the phylum Firmicutes. 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.[2] 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.[2]

Physiology and classification

Enterococci are facultative anaerobic organisms, i.e., they are capable of cellular respiration in both oxygen-rich and oxygen-poor environments.[3] Though they are not capable of forming spores, enterococci are tolerant of a wide range of environmental conditions: extreme temperature (10-45°C), pH (4.5-10.0) and high sodium chloride concentrations.[4]

Enterococci typically exhibit gamma-hemolysis on sheep's blood agar.[5]

History

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.[6]

Pathology

Important clinical infections caused by Enterococcus include urinary tract infections, bacteremia, bacterial endocarditis, diverticulitis, and meningitis.[4][5] Sensitive strains of these bacteria can be treated with ampicillin, penicillin and vancomycin.[7] Urinary tract infections can be treated specifically with nitrofurantoin, even in cases of vancomycin resistance.[8]

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.[5] 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.[4] Other developed countries, such as the UK, have been spared this epidemic, and, in 2005, Singapore managed to halt an epidemic of VRE.[9] VRE may be treated with quinupristin/dalfopristin (Synercid) with response rates of approximately 70%.[10] Tigecycline has also been shown to have anti-enterococcal activity as has rifampicin.[citation needed]

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.[11] New epidemiological evidence has shown that enterococci are major infectious agent in chronic bacterial prostatitis[citation needed]. Enterococci are able to form biofilm in the prostate gland making their eradication difficult.

Enterococcus
Classification and external resources
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ICD-9-CM 041.04
Patient UK Enterococcus
[[[d:Lua error in Module:Wikidata at line 863: attempt to index field 'wikibase' (a nil value).|edit on Wikidata]]]

Water quality

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.[12] In 2004, Enterococci sp. took the place of fecal coliforms as the new USA federal standard for water quality at public saltwater beaches and E. coli at freshwater beaches.[13] It is believed to provide a higher correlation than fecal coliform with many of the human pathogens often found in city sewage.[14]

References

  1. LPSN entry for Enterococcus
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