Enterococcus

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Enterococcus
Enterococcus histological pneumonia 01.png
Enterococcus sp. infection in pulmonary tissue
Scientific classification
Kingdom: Bacteria
Division: Firmicutes
Class: Bacilli
Order: Lactobacillales
Family: Enterococcaceae
Genus: Enterococcus
(ex Thiercelin & Jouhaud 1903)
Schleifer & Kilpper-Bälz 1984
Species

E. malodoratus
E. avium
E. durans
E. faecalis
E. faecium
E. gallinarum
E. hirae
E. solitarius
etc.

Enterococcus is a 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.[1] 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.[1]

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.[2] 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.[3]

Enterococci typically exhibit gamma-hemolysis on sheep's blood agar.[4]

History[edit]

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.[5]

Pathology[edit]

Important clinical infections caused by Enterococcus include urinary tract infections, bacteremia, bacterial endocarditis, diverticulitis, and meningitis.[3][4] Sensitive strains of these bacteria can be treated with ampicillin, penicillin and vancomycin.[6] Urinary tract infections can be treated specifically with nitrofurantoin, even in cases of vancomycin resistance.[7]

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.[4] 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.[3] Other developed countries, such as the UK, have been spared this epidemic, and, in 2005, Singapore managed to halt an epidemic of VRE.[8] VRE may be treated with quinupristin/dalfopristin (Synercid) with response rates of approximately 70%.[9] Tigecycline has also been shown to have anti-enterococcal activity as has rifampicin.[1]

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.[10] 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
ICD-9 041.04

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

References[edit]

  1. ^ a b Gilmore MS, et al., ed. (2002). The Enterococci: Pathogenesis, Molecular Biology, and Antibiotic Resistance. Washington, D.C.: ASM Press. ISBN 978-1-55581-234-8. 
  2. ^ Fischetti VA, Novick RP, Ferretti JJ, Portnoy DA, Rood JI, ed. (2000). Gram-Positive Pathogens. ASM Press. ISBN 1-55581-166-3. 
  3. ^ a b c Fisher K, Phillips C (June 2009). "The ecology, epidemiology and virulence of Enterococcus". Microbiology 155 (Pt 6): 1749–57. doi:10.1099/mic.0.026385-0. PMID 19383684. 
  4. ^ a b c Ryan KJ, Ray CG, ed. (2004). Sherris Medical Microbiology (4th ed.). McGraw Hill. pp. 294–5. ISBN 0-8385-8529-9. 
  5. ^ Schleifer KH; Kilpper-Balz R (1984). "Transfer of Streptococcus faecalis and Streptococcus faecium to the genus Enterococcus nom. rev. as Enterococcus faecalis comb. nov. and Enterococcus faecium comb. nov.". Int. J. Sys. Bacteriol. 34: 31–34. doi:10.1099/00207713-34-1-31. 
  6. ^ Pelletier LL Jr. (1996). Microbiology of the Circulatory System. in: Baron's Medical Microbiology (Baron S et al., eds.) (4th ed.). Univ of Texas Medical Branch. ISBN 0-9631172-1-1. 
  7. ^ Zhanel GG, Hoban DJ, Karlowsky JA (January 2001). "Nitrofurantoin is active against vancomycin-resistant enterococci". Antimicrob. Agents Chemother. 45 (1): 324–6. doi:10.1128/AAC.45.1.324-326.2001. PMC 90284. PMID 11120989. 
  8. ^ Kurup, Asok; Chlebicki, M.P.; Ling, M.L.; Koh, T.H.; Tan, K.Y.; Lee, L.C.; Howe, K.B.M. (April 2008). "Control of a hospital-wide vancomycin-resistant Enterococci outbreak". American Journal of Infection Control 36 (3): 206–211. doi:10.1016/j.ajic.2007.06.005. Retrieved 26 November 2014. 
  9. ^ Tünger A, Aydemir S, Uluer S, Cilli F (2004). "In vitro activity of linezolid & quinupristin/dalfopristin against Gram-positive cocci". Indian J Med Res 120 (6): 546–52. PMID 15654141. 
  10. ^ Guardado R, Asensi V, Torres JM et al. (2006). "Post-surgical enterococcal meningitis: clinical and epidemiological study of 20 cases". Scand. J. Infect. Dis. 38 (8): 584–8. doi:10.1080/00365540600606416. PMID 16857599. 
  11. ^ "Clean Water Branch". Hawaii State Department of Health. Retrieved 2012-05-18. 
  12. ^ "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. 
  13. ^ Jin G, Jeng HW, Bradford H, Englande AJ (2004). "Comparison of E. coli, enterococci, and fecal coliform as indicators for brackish water quality assessment". Water Environ. Res. 76 (3): 245–55. doi:10.2175/106143004X141807. PMID 15338696.