Streptococcus
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robot Adding: [[la:Streptococcus]]
{{Taxobox
| color = lightgrey
| name = ''Streptococcus''
| image = Streptococcus.jpg
| image_width = 270px
| regnum = [[Eubacteria]]
| phylum = [[Firmicutes]]
| classis = [[Bacilli]]
| ordo = [[Lactobacillales]]
| familia = [[Streptococcaceae]]
| genus = '''''Streptococcus'''''
| genus_authority = Rosenbach, [[1884]]
| subdivision_ranks = Species
| subdivision =
''[[Streptococcus agalactiae|S. agalactiae]]''<br/>
''[[Streptococcus aginosus|S. aginosus]]''<br/>
''[[Streptococcus bovis|S. bovis]]''<br/>
''[[Streptococcus canis|S. canis]]''<br/>
''[[Streptococcus mutans|S. mutans]]''<br/>
''[[Streptococcus oralis|S. oralis]]''<br/>
''[[Streptococcus peroris|S. peroris]]''<br/>
''[[Streptococcus pneumoniae|S. pneumoniae]]''<br/>
''[[Streptococcus pyogenes|S. pyogenes]]''<br/>
''[[Streptococcus ratti|S. ratti]]''<br/>
''[[Streptococcus salivarius|S. salivarius]]''<br/>
''[[Streptococcus sanguinis|S. sanguinis]]''<br/>
''[[Streptococcus sobrinus|S. sobrinus]]''<br/>
''[[Streptococcus parasanguinis|S. parasanguinis]]''<br/>
''[[Streptococcus suis|S. suis]]''<br/>
''[[Streptococcus thermophilus|S. thermophilus]]''<br/>
''[[Streptococcus vestibularis|S. vestibularis]]''<br/>
''[[Streptococcus viridans]]''<br/>
''[[Streptococcus uberis]]''<br/>
etc.
}}
'''''Streptococcus''''' is a [[genus]] of [[sphere|spherical]] [[Gram-positive]] [[bacterium|bacteria]], belonging to the [[phylum (biology)|phylum]] [[Firmicutes]]<ref name=Sherris>{{cite book | author = Ryan KJ; Ray CG (editors) | title = Sherris Medical Microbiology | edition = 4th ed. | publisher = McGraw Hill | year = 2004 | id = ISBN 0-8385-8529-9 }}</ref> and the [[lactic acid bacteria]] group. [[Cell division|Cellular division]] occurs along a single [[Coordinate axis|axis]] in these bacteria, and thus they grow in chains or pairs, hence the name — from [[Greek language|Greek]] στρεπτος ''streptos'', meaning easily bent or twisted, like a chain. Contrast this with [[Staphylococcus|staphylococci]], which divide along multiple axes and generate grape-like clusters of [[cell (biology)|cell]]s.
Streptococci are [[oxidase]]– and [[catalase]]–negative.
==Pathogenesis==
In addition to [[streptococcal pharyngitis|strep throat]], certain ''Streptococcus'' species are responsible for many cases of [[meningitis]], [[bacterial pneumonia]], [[endocarditis]], [[erysipelas]] and [[necrotizing fasciitis]] (the 'flesh-eating' bacterial infections). However, many streptococcal species are non-pathogenic. Streptococci are also part of the normal [[Commensalism|commensal]] [[flora (microbiology)|flora]] of the mouth, skin, intestine, and upper respiratory tract of humans.
As a rule, individual species of ''Streptococcus'' are classified based on their [[Hemolysis (microbiology)|hemolytic]] properties (breakdown of red blood cells in a laboratory).<ref name=Baron>{{cite book | author = Patterson MJ | title = Streptococcus. ''In:'' Baron's Medical Microbiology ''(Baron S ''et al'', eds.)| edition = 4th ed. | publisher = Univ of Texas Medical Branch | year = 1996 | id = [http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=mmed.section.824 (via NCBI Bookshelf)] ISBN 0-9631172-1-1 }} </ref> Alpha hemolysis is caused by a reduction of iron in hemoglobin, giving it a greenish color on blood agar. Beta-only hemolysis is complete rupture of red blood cells, giving distinct, wide, clear areas around bacterial colonies on blood agar. Other streptococci are labeled as gamma hemolytic, actually a misnomer, as no hemolysis takes place.
Beta-hemolytic streptococci are further characterised via the [[Serovar|Lancefield serotyping]] - based on specific carbohydrates in the bacterial cell wall.<ref name=Facklam_2002>{{cite journal | author=Facklam R | title=What happened to the streptococci: overview of taxonomic and nomenclature changes | journal=Clin Microbiol Rev | year=2002 | pages=613–30 | volume=15 | issue=4 | pmid=12364372 | doi = 10.1128/CMR.15.4.613-630.2002 <!--Retrieved from CrossRef by DOI bot-->}}</ref> These are named Lancefield groups A to T, although some species, such as ''S. pneumoniae'', do not express Lancefield antigens. See the related article on [[Rebecca Lancefield]]. In the medical setting, the most important groups are the alpha-hemolytic streptococci, ''S. pneumoniae'' and ''Streptococcus'' Viridans-group, and the beta-hemolytic streptococci of Lancefield groups A and B (also known as “Group A Strep” and “Group B Strep”).
===Alpha-Hemolytic Streptococcus===
====Pneumococci====
*''[[Streptococcus pneumoniae|S. pneumoniae]]'', a leading cause of bacterial [[pneumonia]], otitis media and [[meningitis]].
====Viridans and Others====
* ''[[Streptococcus mutans|S. mutans]]'', a contributor to [[dental caries]]
* ''[[Streptococcus viridans|S. viridans]]'', a cause of [[endocarditis]] and [[Tooth abscess|dental abscesses]]
* ''[[Streptococcus thermophilus|S. thermophilus]]'', used in the manufacture of some cheeses and yogurts
* ''[[Streptococcus constellatus|S. constellatus]]'', occasional human pathogen, notable as colonies grown on blood [[agar]] smell strongly of caramel
===Beta-Hemolytic Streptococci===
====Group A ====
''[[Streptococcus pyogenes|S. pyogenes]]'' (also known as ''GAS'') is the causative agent in [[Group A streptococcal infection]]s, (''GAS'') including [[streptococcal pharyngitis]] ("strep throat"), acute [[rheumatic fever]], [[scarlet fever]], acute [[glomerulonephritis]] and [[necrotizing fasciitis]]. If [[strep throat]] is not treated, it can develop into [[rheumatic fever]], a disease that affects the [[joint]]s and [[heart valve]]s. Other ''Streptococcus'' species may also possess the Group A antigen, but human infections by non-''S. pyogenes'' GAS strains (some ''S. dysgalactiae'' subsp. ''equisimilis'' and ''S. anginosus'' Group strains) appear to be uncommon.
Group A Strep infection is generally diagnosed with a [[Rapid Strep Test]] or by culture.
====Group B ====
''[[Streptococcus agalactiae|S. agalactiae]]'', or ''GBS'', causes [[pneumonia]] and [[meningitis]] in [[neonate]]s and the [[elderly]], with occasional systemic [[bacteremia]]. They can also colonize the intestines and the female reproductive tract, increasing the risk for premature rupture of membranes and transmission to the infant. The American College of Obstetricians and Gynecologists, American Academy of Pediatrics and the [[Centers for Disease Control]] recommend all pregnant women between 35 and 37 weeks gestation should be tested for GBS. Women who test positive should be given prophylactic antibiotics during labor, which will usually prevent transmission to the infant.<ref name=Schrag_2002>{{cite journal |author=Schrag S, Gorwitz R, Fultz-Butts K, Schuchat A |title=Prevention of perinatal group B streptococcal disease. Revised guidelines from CDC |journal=MMWR Recomm Rep |volume=51 |issue=RR-11 |pages=1–22 |year=2002 |pmid=12211284}}</ref> In the [[United Kingdom|UK]], clinicians have been slow to implement the same standards as the [[United States of America|US]], [[Australia]] and [[Canada]]. In the UK, only 1% of maternity units test for the presence of Group B Strep.<ref name=RCOG_2003>{{cite paper | author = Hughes, RG, et al. | title = Prevention of Early Onset Neonatal Group B Streptococcal Disease | publisher = Royal College of Obstetricians and Gynaecologists | url = http://www.rcog.org.uk/index.asp?PageID=520 | format = [[HTML]]}}</ref> Although The Royal College of Obstetricians and Gynaecologists issued risk-based guidelines in 2003 (due for review 2006), the implentation of these guidelines has been patchy. Some groups feel that as a result over 75 infants in the UK die each year of GBS related disease and another 600 or so suffer serious infection, most of which could be prevented <ref name=GBSS_2007>{{cite web | title = Group B Strep Support Home Page | publisher = Group B Strep Support | date = 2007-01-09 | url = http://www.gbss.org.uk/ | format = [[HTML]]}}</ref> however this is yet to be substantiated by RCT in the UK setting and, given the evidence for the efficacy of testing and treating from other countries, it may be that the large-scale trial necessary would receive neither funding nor ethics approval.<ref name=Arjb1_2007>{{cite web | title = RCOG: Preventing group B streptococcus infection in new born babies | publisher = RCOG | date = 2006-02 | url = http://www.rcog.org.uk/index.asp?PageID=1400#national | format = [[HTML]]}}</ref>
====Group C ====
Includes ''S. equi'', which causes [[strangles]] in horses,<ref name=Harrington_2002>{{cite journal |author=Harrington D, Sutcliffe I, Chanter N |title=The molecular basis of Streptococcus equi infection and disease |journal=Microbes Infect |volume=4 |issue=4 |pages=501–10 |year=2002 |pmid=11932201 | doi = 10.1016/S1286-4579(02)01565-4 <!--Retrieved from CrossRef by DOI bot-->}}</ref> and ''[[Streptococcus zooepidemicus|S. zooepidemicus]]'', which causes infections in several species of mammals including cattle and horses. This can also cause death in chickens and [[moose]]. Many mountaineers from Canada have found corpses of moose lying in the middle of the road; post-mortem tests have found group c streptococcus in their blood.
====Group D (Enterococci) *variable in hemolysis====
Many former Group D streptococci have been reclassified and placed in the genus ''[[Enterococcus]]'' (includes ''S. faecalis'', ''S. faecium'', ''S. durans'', and ''S. avium'').<ref name=Ruoff_1990>{{cite journal | author=Ruoff KL | title=Recent taxonomic changes in the genus Enterococcus | journal=Eur J Clin Microbiol Infect Dis | year=1990 | pages=75–9 | volume=9 | issue=2 | pmid= 2108030 | doi = 10.1007/BF01963630 <!--Retrieved from CrossRef by DOI bot-->}}</ref> For example, ''Streptococcus faecalis'' is now ''[[Enterococcus faecalis]]''.
The remaining non-enterococcal Group D strains include ''[[Streptococcus bovis]]'' and ''[[Streptococcus equinus]]''.
===Non-Hemolytic Streptococci===
Non-hemolytic streptococci rarely cause disease. However, weakly hemolytic group D beta-hemolytic streptococci and ''[[Listeria monocytogenes]]'' should not be confused with non-hemolytic
streptococci.
==References==
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==External links==
*[http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5111a1.htm Prevention of Perinatal Group B Streptococcal Disease] August 16, 2002 MMWR 2000;49:228-232.
*[http://www.strepb.ca/home.htm The Canadian Strep B Foundation]
*[http://www.gbss.org.uk The UK Group B Strep Support charity]
[[Category:Streptococcaceae]]
[[Category:Gut flora]]
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