Enterococcus Explained

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.[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.

Physiology and classification

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 (4.6–9.9), and high sodium chloride concentrations.[3]

Enterococci exhibit variable hemolysis on blood agar. Differences occur between species, and between strains of species. More virulent organisms are more likely to exhibit alpha (partial) or beta (complete) hemolysis than less virulent specimens of Enterococcus, which frequently exhibit gamma (absent) hemolysis.[4]

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.[5]

Evolution

This genus appears to have evolved to .[6]

Pathology

Important clinical infections caused by Enterococcus include urinary tract infections (see Enterococcus faecalis), bacteremia, bacterial endocarditis, diverticulitis, meningitis, and spontaneous bacterial peritonitis.[7] [8] Sensitive strains of these bacteria can be treated with ampicillin, penicillin and vancomycin.[9] Urinary tract infections can be treated specifically with nitrofurantoin, even in cases of vancomycin resistance.[10]

Meningitis

See main article: Meningitis. 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.[12] Enterococci are able to form biofilm in the prostate gland, making their eradication difficult. Cases of enterococcal meningitis, in the absence of trauma or surgery, should raise suspicion of an underlying intestinal pathology (e.g., strongyloidiasis).[13]

Antibacterial resistance

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. 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. Other developed countries, such as the UK, have been spared this epidemic, and, in 2005, Singapore managed to halt an epidemic of VRE.[14] Although quinupristin/dalfopristin (Synercid) was previously indicated for treatment of VRE in the USA, the FDA approval for this indication has since been retracted.[15] 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.[16] [17] Tigecycline has also been shown to have antienterococcal activity, as has rifampicin.[18]

Bacillus haynesii CD223 and Advenella mimigardefordensis SM421 can inhibit the growth of Enterococcus spp. [19]

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.[20] In 2004, measurement of enterococci took the place of fecal coliforms as the new American 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]

Notes and References

  1. Book: The Enterococci: Pathogenesis, Molecular Biology, and Antibiotic Resistance . ASM Press . Washington, D.C. . 2002 . Gilmore MS . 978-1-55581-234-8. etal.
  2. Book: Fischetti VA, Novick RP, Ferretti JJ, Portnoy DA, Rood JI . Gram-Positive Pathogens . ASM Press . 2000 . 1-55581-166-3.
  3. Fisher K, Phillips C . The ecology, epidemiology and virulence of Enterococcus . Microbiology . 155 . Pt 6 . 1749–1757 . June 2009 . 19383684 . 10.1099/mic.0.026385-0 . free .
  4. Semedo T, Almeida Santos M, Martins P, Silva Lopes MF, Figueiredo Marques JJ, Tenreiro R, Barreto Crespo MT . Comparative study using type strains and clinical and food isolates to examine hemolytic activity and occurrence of the cyl operon in enterococci . Journal of Clinical Microbiology . 41 . 6 . 2569–2576 . June 2003 . 12791882 . 156526 . 10.1128/jcm.41.6.2569-2576.2003 .
  5. Schleifer KH, Kilpper-Balz R . 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. Syst. Bacteriol.. 1984 . 34 . 31–34 . 10.1099/00207713-34-1-31 . free .
  6. Lebreton F, Manson AL, Saavedra JT, Straub TJ, Earl AM, Gilmore MS . Tracing the Enterococci from Paleozoic Origins to the Hospital . Cell . 169 . 5 . 849–861.e13 . May 2017 . 28502769 . 5499534 . 10.1016/j.cell.2017.04.027 .
  7. Book: Ryan KJ, Ray CG . Sherris Medical Microbiology . 4th . 294–5 . McGraw Hill . 2004 . 0-8385-8529-9 .
  8. Fiore M, Maraolo AE, Gentile I, Borgia G, Leone S, Sansone P, Passavanti MB, Aurilio C, Pace MC . Current concepts and future strategies in the antimicrobial therapy of emerging Gram-positive spontaneous bacterial peritonitis . World Journal of Hepatology . 9 . 30 . 1166–1175 . October 2017 . 29109849 . 5666303 . 10.4254/wjh.v9.i30.1166 . free .
  9. Book: Pelletier Jr LL . Microbiology of the Circulatory System. Baron's Medical Microbiology . Albrecht T, Baron S . 4th . Univ of Texas Medical Branch . 1996 . 21413321. 0-9631172-1-1 .
  10. Zhanel GG, Hoban DJ, Karlowsky JA . Nitrofurantoin is active against vancomycin-resistant enterococci . Antimicrobial Agents and Chemotherapy . 45 . 1 . 324–326 . January 2001 . 11120989 . 90284 . 10.1128/AAC.45.1.324-326.2001 .
  11. Guardado R, Asensi V, Torres JM, Pérez F, Blanco A, Maradona JA, Cartón JA . Post-surgical enterococcal meningitis: clinical and epidemiological study of 20 cases . Scandinavian Journal of Infectious Diseases . 38 . 8 . 584–588 . 2006 . 16857599 . 10.1080/00365540600606416 . 24189202 .
  12. Web site: Enterococcus sp rRNA [Presence] in Specimen by Probe ]. 5001-3 . Logical Observation Identifiers Names and Codes (LOINC) . Regenstrief Institute, Inc. .
  13. Cosimi L, Di Bella S, Luzzati R, Simeth CT, Pinamonti M, Cominotto F, Sisto UG . Enterococcal meningitis associated with Strongyloides infection: a case report and literature review . Le Infezioni in Medicina . 31 . 4 . 583–590 . 2023-12-01 . 38075422 . 10705849 . 10.53854/liim-3104-18 .
  14. Kurup A, Chlebicki MP, Ling ML, Koh TH, Tan KY, Lee LC, Howe KB . Control of a hospital-wide vancomycin-resistant Enterococci outbreak . American Journal of Infection Control . 36 . 3 . 206–211 . April 2008 . 18371517 . 7115253 . 10.1016/j.ajic.2007.06.005 .
  15. Batts DH, Lavin BS, Eliopoulos GM . Quinupristin/dalfopristin and linezolid: spectrum of activity and potential roles in therapy--a status report . Current Clinical Topics in Infectious Diseases . 21 . 227–251 . 2001 . 11572153 .
  16. Collins LA, Malanoski GJ, Eliopoulos GM, Wennersten CB, Ferraro MJ, Moellering RC . In vitro activity of RP59500, an injectable streptogramin antibiotic, against vancomycin-resistant gram-positive organisms . Antimicrobial Agents and Chemotherapy . 37 . 3 . 598–601 . March 1993 . 8460927 . 187713 . 10.1128/aac.37.3.598 .
  17. Singh KV, Weinstock GM, Murray BE . 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 . June 2002 . 12019099 . 127256 . 10.1128/AAC.46.6.1845-1850.2002 . free .
  18. Web site: Enterococcus sp DNA [Presence] by NAA with probe detection in Positive blood culture ]. 92784-8 . Logical Observation Identifiers Names and Codes (LOINC) . Regenstrief Institute, Inc. .
  19. Rahman MM, Paul SI, Rahman A, Haque MS, Ador MA, Foysal MJ, Islam MT, Rahman MM . Suppression of Streptococcosis and Modulation of the Gut Bacteriome in Nile Tilapia (Oreochromis niloticus) by the Marine Sediment Bacteria Bacillus haynesii and Advenella mimigardefordensis . Microbiology Spectrum . 10 . 6 . e0254222 . December 2022 . 36453920 . 9769507 . 10.1128/spectrum.02542-22 . Rogovskyy AS, Weththasinghe P, Rodriguez-Estrada U .
  20. Web site: Clean Water Branch . Hawaii State Department of Health . 2012-05-18 . dead . https://web.archive.org/web/20111111031411/http://gen.doh.hawaii.gov/sites/har/AdmRules1/11-54.pdf . 2011-11-11 .
  21. Water Quality Standards for Coastal and Great Lakes Recreation Waters; Final Rule. Federal Register. 16 November 2004. 69. 220. 67218–67243. 26 November 2014.
  22. Jin G, Jeng HW, Bradford H, Englande AJ . Comparison of E. coli, enterococci, and fecal coliform as indicators for brackish water quality assessment . Water Environment Research . 76 . 3 . 245–255 . 2004 . 15338696 . 10.2175/106143004X141807 . 2004WaEnR..76..245J . 35780753 .

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