streptococcus
American Heritage Dictionary:
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strep·to·coc·cus
(strĕp'tə-kŏk'əs) 
n., pl., -coc·ci (-kŏk'sī, -kŏk'ī).
A round to ovoid, gram-positive, often pathogenic bacterium of the genus Streptococcus that occurs in pairs or chains, many species of which destroy red blood cells and cause various diseases in humans, including erysipelas, scarlet fever, and strep throat.
n., pl., -coc·ci (-kŏk'sī, -kŏk'ī).
A round to ovoid, gram-positive, often pathogenic bacterium of the genus Streptococcus that occurs in pairs or chains, many species of which destroy red blood cells and cause various diseases in humans, including erysipelas, scarlet fever, and strep throat.
Britannica Concise Encyclopedia:
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streptococcus
Any of the spheroidal bacteria that make up the genus Streptococcus. The cells characteristically group together in chains resembling a string of beads. Streptococci are gram-positive ( gram stain) and stationary and do not require oxygen. Some species cause infections, including rheumatic fever, scarlet fever, strep throat, and tonsillitis. Others are used in commercial starters for the production of butter, cultured buttermilk, and certain cheeses. pneumococcus.
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McGraw-Hill Science & Technology Encyclopedia:
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Streptococcus
A large genus of spherical or ovoid bacteria that are characteristically arranged in pairs or in chains resembling strings of beads. Many of the streptococci that constitute part of the normal flora of the mouth, throat, intestine, and skin are harmless commensal forms; other streptococci are highly pathogenic. The cells are gram-positive and can grow either anaerobically or aerobically, although they cannot utilize oxygen for metabolic reactions. Glucose and other carbohydrates serve as sources of carbon and energy for growth. All members of the genus lack the enzyme catalase. Streptococci can be isolated from humans and other animals.
Streptococcus pyogenes is well known for its participation in many serious infections. It is a common cause of throat infection, which may be followed by more serious complications such as rheumatic fever, glomerulonephritis, and scarlet fever. Other beta-hemolytic streptococci participate in similar types of infection, but they are usually not associated with rheumatic fever and glomerulonephritis. Group B streptococci, which are usually beta-hemolytic, cause serious infections in newborns (such as meningitis) as well as in adults. Among the alpha-hemolytic and nonhemolytic streptococci, S. pneumoniae is an important cause of pneumonia and other respiratory infections. Vaccines that protect against infection by the most prevalent capsular serotypes are available. The viridans streptococci comprise a number of species commonly isolated from the mouth and throat. Although normally of low virulence, these streptococci are capable of causing serious infections (endocarditis, abcesses). See also Pneumonia.
Columbia Encyclopedia:
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Streptococcus
streptococcus (strĕp'təkŏk'əs), any of a group of gram-positive bacteria, genus Streptococcus, some of which cause disease. Streptococci are spherical and divide by fission, but they remain attached and so grow in beadlike chains. The incidence and severity of streptococcal diseases decreased dramatically after the introduction of antibiotics (penicillin, erythromycin, and selected cephalosporins are all effective against the organisms), but the medical community was shaken by the arrival in the late 1980s of several severe forms of streptococcal infection and by the emergence of several drug-resistant strains (see drug resistance).
Types of Streptococci
Streptococci are classified into the alpha, beta, or gamma groups, according to their action on blood cells. Streptococci of the alpha group (e.g., the viridans and S. pneumoniae) cause some destruction (hemolysis) of red blood cells. The beta group are more destructive of red blood cells; they also produce toxic substances that affect white blood cells and the clotting properties of blood. Members of these two groups are sometimes called hemolytic (red blood cell-destroying) streptococci. The beta-hemolytic streptococci are often further classified into lettered groups, called Lancefield groups for R. C. Lancefield, the scientist who originated the scheme in the 1930s. Group A hemolytic streptococci are responsible for most human streptococcal disease; group B hemolytic streptococci can cause serious problems in newborns. The gamma group, or nonhemolytic group, does not affect red blood cells. Enterococci (usually harmless bacteria that inhabit the intestines) and lactococci (bacteria used in starter cultures in the production of fermented dairy products) used to be considered a part of the Streptococcus genus but are now placed in their own genera.
S. pneumoniae and Viridans Infections
The viridans are normal inhabitants of the body and are usually harmless; however, they can contribute to tooth decay. Streptococcus pneumoniae is the most common cause of otitis media in children. It can also cause meningitis and pneumonia. The S. pneumoniae diseases are sometimes referred to as pneumococcal diseases. The development of drug-resistant strains of pneumococci has caused concern in the medical community. Vaccination against pneumococcal pneumonia is recommended for very young children and older persons; the vaccine inoculates against the most prevalent strains of S. pneumoniae.
Group A Streptococcal Infections
Group A hemolytic streptococci cause over a dozen diseases, including some pneumonias, erysipelas (a generalized body infection), upper respiratory infections, wound infections, and puerperal fever. Scarlet fever is also a streptococcal, or strep, infection; the rash is a response to a toxin produced by the bacteria that cause strep throat. Rheumatic fever follows an initial Group A streptococcal infection: proteins of the streptococcal cells stimulate antibody formation by the body (see immunity), and these antistreptococcal antibodies are believed to react with and damage many tissues of the body, especially heart muscle. Kidney disease (acute glomerulonephritis) is another complication of streptococcal infections. Some extremely serious Group A streptococcal infections began to emerge or reemerge in the late 1980s. Streptococcal toxic shock syndrome is a rapidly progressing infection, similar to septicemia or toxic shock syndrome, that usually infects people in their 20s or 30s. It causes blood pressure to fall rapidly and organs to fail. Necrotizing fasciitis is a quickly spreading infection of the flesh and muscle caused by toxins released by S. pyrogenes. Such bacteria are popularly called "flesh-eating bacteria."
Group B Streptococcal Infections
Group B streptococci are a common cause of infection in babies, pregnant women, the elderly, and immunologically compromised adults. They are especially serious in newborns, in whom they can cause sepsis, meningitis, or pneumonia. Group B streptococci are often present in people who show no symptoms of disease; these people are said to be "colonized." Many infants are colonized before or during birth by mothers who unknowingly carry the bacteria. A small percentage of these develop disease, which can be life-threatening or can lead to lifelong neurological problems.
Bibliography
See M. P. Starr et al., ed., The Prokaryotes: A Handbook on Habitats, Isolation and Identification of Bacteria (1981).
Dictionary of Cultural Literacy: Health:
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streptococcus
(strep-tuh-kok-uhs)
A category of bacteria that can cause various infections in humans, including scarlet fever and strep throat.
Oxford Dictionary of Biochemistry:
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Streptococcus
a genus of Gram-positive, facultatively or obligately anaerobic cocci or coccoid bacteria that produce streptokinase, streptolysin, and streptodornase.
| Stokes' shift, Stokes' loss, Stokes' law of viscosity | |
| Streptomyces, Stuart factor, Student's |
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categories related to 'streptococcus'
- Diagnostic Terminology - streptococcus: any of several spherical, chain-forming pathogenic bacteria, mostly saprophytes
Wikipedia on Answers.com:
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Streptococcus
Not to be confused with Staphylococcus.
| Streptococcus | |
|---|---|
 |
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| Scientific classification | |
| Kingdom: | Bacteria |
| Phylum: | Firmicutes |
| Class: | Coccus[1] |
| Order: | Lactobacillales |
| Family: | Streptococcaceae |
| Genus: | Streptococcus Rosenbach, 1884 |
| Species | |
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S. agalactiae |
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Streptococcus is a genus of spherical Gram-positive bacteria belonging to the phylum Firmicutes[2] and the lactic acid bacteria group. Cellular division occurs along a single axis in these bacteria, and thus they grow in chains or pairs, hence the name — from Greek στρεπτος streptos, meaning easily bent or twisted, like a chain (twisted chain). Contrast this with staphylococci, which divide along multiple axes and generate grape-like clusters of cells. Most streptococci are oxidase- and catalase-negative, and many are facultative anaerobes.
In 1984, many organisms formerly considered Streptococcus were separated out into the genera Enterococcus and Lactococcus.[3]
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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 nonpathogenic. Indeed, streptococci are a necessary ingredient in Emmentaler ("Swiss") cheese. Streptococci are also part of the normal commensal microbiome of the mouth, skin, intestine, and upper respiratory tract of humans.
As a rule, individual species of Streptococcus are classified based on their hemolytic properties.[4] Alpha hemolysis is caused by an oxidation of iron in hemoglobin, giving it a greenish color on blood agar. Beta 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.
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”). Beta-hemolytic streptococci are further characterised via the Lancefield serotyping – based on specific carbohydrates in the bacterial cell wall.[5] These are named Lancefield groups A to V (except I and J).
Alpha-hemolytic
Pneumococci
- S. pneumoniae (sometimes called Pneumococcus), is a leading cause of bacterial pneumonia and occasional etiology of otitis media, sinusitis, meningitis and peritonitis.
Inflammation is thought to be the major cause of how pneumococcus causes disease, hence the inflammatory nature of the diagnoses associated with it [ above ].
The Viridans group: alpha-hemolytic
- S. mutans, a contributor to dental caries
- S. mitis, mostly found around cheek region
- S. sanguinis, no preference of locations
- S. salivarius, mostly found on the dorsal side of the tongue
- S. salivarius ssp. thermophilus, used in the manufacture of some cheeses and yogurts
- S. constellatus, occasional human pathogen, notable as colonies grown on blood agar smell strongly of caramel
Beta-hemolytic
Group A
S. pyogenes, also known as Group A Streptococcus (GAS), is the causative agent in Group A streptococcal infections, including streptococcal pharyngitis ("strep throat"), acute rheumatic fever, scarlet fever, acute glomerulonephritis and necrotizing fasciitis. Strep. pyogenes is the other major cause of streptococcal infection in humans, after pneumococcus. However, rather than being directly invasive and inflammatory, it seems to cause local infection, but then its other actions are via toxins: whether affecting kidneys in post strep glomerulonephritis, heart valves in rheumatic fever, the scarlet skin of scarlet fever or dissolving tissue in necrotizing fasciitis. 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 Streptococcus infection is generally diagnosed with a Rapid Strep Test or by culture. Rheumatic fever, a disease that affects the joints, kidneys and heart valves, is a consequence of untreated strep A infection caused not by the bacterium itself. Rheumatic fever is caused by the antibodies created by the immune system to fight off the infection cross-reacting with other proteins in the body. This cross-reaction causes the body to essentially attack itself and leads to the damage above.
Group B
S. agalactiae, or GBS, causes pneumonia and meningitis in neonates 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 that 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.[6] In the UK, clinicians have been slow to implement the same standards as the US, Australia and Canada. In the UK, only 1% of maternity units test for the presence of Group B Streptococcus.[7] Although the Royal College of Obstetricians and Gynaecologists issued risk-based guidelines in 2003 (due for review 2006), the implementation of these guidelines has been patchy. 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;[8] however, this is yet to be substantiated by randomized, controlled trial 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.[9]
Group C
This group includes S. equi, which causes strangles in horses,[10] and S. zooepidemicus - S. equi is a clonal descendent or biovar of the ancestral S. zooepidemicus - which causes infections in several species of mammals, including cattle and horses. Streptococcus dysgalactiae is also a member of Group C, β-haemolytic streptococci that can cause pharyngitis and other pyogenic infections similar to Group A streptococci.
Group D (enterococci)
Many former Group D streptococci have been reclassified and placed in the genus Enterococcus (including Enterococcus faecalis, Enterococcus faecium, Enterococcus durans, and Enterococcus avium).[11] For example, Streptococcus faecalis is now Enterococcus faecalis.
The remaining nonenterococcal Group D strains include Streptococcus bovis and Streptococcus equinus.
Nonhemolytic streptococci rarely cause illness. However, weakly hemolytic group D beta-hemolytic streptococci and Listeria monocytogenes (which is actually a Gram-positive bacillus) should not be confused with nonhemolytic streptococci.
Group F streptococci
Group F streptococci were first described in 1934 by Long and Bliss amongst the "minute haemolytic streptococci".[12] They are also known as Streptococcus anginosus (according to the Lancefield classification system) or as members of the S. milleri group (according to the European system).
Group G streptococci
These streptococci are usually, but not exclusively, beta-hemolytic. Streptococcus canis is an example of a GGS which is typically found on animals, but can cause infection in humans.
Treatment
- See List of antibiotics.
See also
References
- ^ "Result of detail taxonomy information". TXSearch Taxonomy Retrieval. DNA Data Bank of Japan. 19 February 2010. http://txsearch.ddbj.nig.ac.jp/txsearch/txsearch.TXSearch?tx_Clas=scientific+name&tx_Name=Streptococcus&tx_Rank=All&tx_Rmax=10&tx_Dcls=yes&tx_Lang=en&tx_Mode=DETAIL&tx_Id=1301&tx_R_Id=0. Retrieved 30 March 2010.
- ^ Ryan KJ, Ray CG, ed. (2004). Sherris Medical Microbiology (4th ed.). McGraw Hill. ISBN 0-8385-8529-9.
- ^ Facklam R (October 2002). "What happened to the streptococci: overview of taxonomic and nomenclature changes". Clin. Microbiol. Rev. 15 (4): 613–30. doi:10.1128/CMR.15.4.613-630.2002. PMC 126867. PMID 12364372. http://cmr.asm.org/cgi/pmidlookup?view=long&pmid=12364372.
- ^ Patterson MJ (1996). Streptococcus. In: Baron's Medical Microbiology (Baron S et al., eds.) (4th ed.). Univ of Texas Medical Branch. (via NCBI Bookshelf) ISBN 0-9631172-1-1.
- ^ Facklam R (2002). "What happened to the streptococci: overview of taxonomic and nomenclature changes". Clin Microbiol Rev 15 (4): 613–30. doi:10.1128/CMR.15.4.613-630.2002. PMC 126867. PMID 12364372. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=126867.
- ^ Schrag S, Gorwitz R, Fultz-Butts K, Schuchat A (2002). "Prevention of perinatal group B streptococcal disease. Revised guidelines from CDC". MMWR Recomm Rep 51 (RR-11): 1–22. PMID 12211284.
- ^ Hughes, RG, et al.. Prevention of Early Onset Neonatal Group B Streptococcal Disease. Royal College of Obstetricians and Gynaecologists. http://www.rcog.org.uk/index.asp?PageID=520.
- ^ "Group B Strep Support Home Page". Group B Strep Support. 2007-01-09. http://www.gbss.org.uk/.
- ^ "RCOG: Preventing group B streptococcus infection in new born babies". RCOG. 2006-02. http://www.rcog.org.uk/index.asp?PageID=1400#national.
- ^ Harrington D, Sutcliffe I, Chanter N (2002). "The molecular basis of Streptococcus equi infection and disease". Microbes Infect 4 (4): 501–10. doi:10.1016/S1286-4579(02)01565-4. PMID 11932201.
- ^ Köhler W (June 2007). "The present state of species within the genera Streptococcus and Enterococcus". International Journal of Medical Microbiology 297 (3): 133–50. doi:10.1016/j.ijmm.2006.11.008. PMID 17400023.
- ^ Withworth JM (1990). "Lancefield group F and related streptococci". J Med Microbiol 33: 131–51.
External links
- Streptococcus genomes and related information at PATRIC, a Bioinformatics Resource Center funded by NIAID
- Prevention of Perinatal Group B Streptococcal Disease August 16, 2002 MMWR 2000;49:228-232.
- The Canadian Strep B Foundation
- The UK Group B Strep Support charity
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