Enterococcus

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Enterococcus is a genus of lactic acid bacteria of the phylum Firmicutes. Members of this genus were classified as Group D Streptococcus until 1984 when genomic DNA analysis indicated that a separate genus classification was appropriate.^[1] Important clinical infections caused by Enterococcus include urinary tract infections, bacteremia, bacterial endocarditis, diverticulitis, and meningitis.^[2] Sensitive strains of these bacteria can be treated with ampicillin and vancomycin.^[3] However, the most important feature of this genus is their high level of endemic antibiotic resistance.

Enterococcus is a genus of lactic acid bacteria of the phylum Firmicutes. Members of this genus were classified as Group D Streptococcus until 1984 when genomic DNA analysis indicated that a separate genus classification was appropriate.^[4] Enterococci are Gram-positive cocci which often occur in pairs (diplococci) and are difficult to distinguish from Streptococci on physical characteristics alone. Two species are common commensal organisms in the intestines of humans: E. faecalis (90-95%) and E. faecium (5-10%). Enterococci are facultative anaerobic organisms, i.e. they prefer the use of oxygen, but they can survive in the absence of oxygen.^[5] They typically exhibit gamma-hemolysis on sheep’s blood agar.

• Bacteremia
• Bacterial endocarditis
• Diverticulitis
• Meningitis^[2]
  • Enterococcal meningitis is a rare complication of neurosurgery. It often requires treatment with intravenous vancomycin; intrathecal vancomycin is often used and it is debatable whether this has any impact on outcome. The removal of any neurological devices is a crucial part of the management of these infections.^[6]
• Urinary tract infection

• Sensitive strains of these bacteria can be treated with ampicillin and vancomycin.^[3]

• From a medical standpoint, the most important feature of this genus is their high level of endemic antibiotic resistance. Some Enterococci are intrinsically resistant to β-lactam-based antibiotics (some penicillins and virtually all cephalosporins) as well as many aminoglycosides.^[2] In the last two decades, particularly virulent strains of Enterococcus which are resistant to vancomycin (Vancomycin-resistant enterococcus, or VRE) have emerged in nosocomial infections of hospitalized patients especially in the US. Other developed countries such as the UK have been spared this epidemic, and in 2005, Singapore managed to halt an epidemic of VRE. VRE may be treated with Quinupristin/dalfopristin (Synercid) with response rates of approximately 70%.^[7]

• The acceptable level of water contamination is very low, for example in the state of Hawaii, with among the strictest tolerances in the United States, the limit for water off its beaches is 7 colony forming units per 100 ml of water, above which the state may post warnings to stay out of the ocean.^[8]
• In 2004, Enterococcus spp. took the place of fecal coliform as the new federal standard for water quality at public beaches. It is believed to provide a higher correlation than fecal coliform with many of the human pathogens often found in sewage.^[9]

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  Scanning Electron Micrograph of Enterococcus species. From Public Health Image Library (PHIL). ^[10]
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  SEM depicts Gram-positiveEnterococcus sp. bacteria From Public Health Image Library (PHIL). ^[10]
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  SEM of Enterococcus species. From Public Health Image Library (PHIL). ^[10]
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  Enterococcus species From Public Health Image Library (PHIL). ^[10]
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  Enterococcus sp. bacteria. From Public Health Image Library (PHIL). ^[10]
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  Photomicrograph reveals cocci-shaped Enterococcus sp. bacteria taken from a pneumonia patient. From Public Health Image Library (PHIL). ^[10]
• 
  SEM depicts Gram-positive Enterococcus sp. bacteria. From Public Health Image Library (PHIL). ^[10]
• 
  3D computer-generated image of a cluster of paired, or diplococcal vancomycin-resistant Enterococcus (VRE) bacteria. From Public Health Image Library (PHIL). ^[10]

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