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1.spherical Gram-positive bacteria occurring in pairs or chains; cause e.g. scarlet fever and tonsillitis
1.(MeSH)A genus of gram-positive, coccoid bacteria whose organisms occur in pairs or chains. No endospores are produced. Many species exist as commensals or parasites on man or animals with some being highly pathogenic. A few species are saprophytes and occur in the natural environment.
Streptococcus‖Strep`to*coc"cus (?), n.; pl. Streptococci (#). [NL., fr. Gr. � pliant, curved + � a grain, seed.] (Biol.) A long or short chain of micrococci, more or less curved.
Infections, Streptococcus pneumoniae • Meningitis, Streptococcus pneumoniae • Other streptococcus as the cause of diseases classified to other chapters • Streptococcus Bacteriophages • Streptococcus Group A • Streptococcus Group B • Streptococcus Group D • Streptococcus Phages • Streptococcus Viridans Group • Streptococcus agalactiae • Streptococcus and staphylococcus as the cause of diseases classified to other chapters • Streptococcus anginosus • Streptococcus anhemolyticus • Streptococcus bovis • Streptococcus constellatus • Streptococcus equi • Streptococcus faecalis • Streptococcus faecium • Streptococcus gordonii • Streptococcus intermedius • Streptococcus lactis • Streptococcus milleri • Streptococcus milleri Group • Streptococcus mitis • Streptococcus mutans • Streptococcus oralis • Streptococcus pneumoniae • Streptococcus pneumoniae Infections • Streptococcus pneumoniae as the cause of diseases classified to other chapters • Streptococcus pyogenes • Streptococcus sanguis • Streptococcus sobrinus • Streptococcus suis • Streptococcus thermophilus • Streptococcus viridans • Streptococcus zooepidemicus • Streptococcus, except group B • Streptococcus, group A, as the cause of diseases classified to other chapters • Streptococcus, group B, as the cause of diseases classified to other chapters • Streptococcus, group D, as the cause of diseases classified to other chapters • Unspecified streptococcus as the cause of diseases classified to other chapters • genus Streptococcus • streptococcus tonsilitis
Cutaneous Streptococcus iniae infection • M protein (Streptococcus) • Pediatric Autoimmune Neuropsychiatric Disorder Associated with Streptococcus • Reports of Streptococcus mitis on the moon • Streptococcus Group N • Streptococcus agalactiae • Streptococcus anginosus • Streptococcus bovis • Streptococcus canis • Streptococcus constellatus • Streptococcus cricetus • Streptococcus dysgalactiae • Streptococcus equi • Streptococcus equinus • Streptococcus equisimilis • Streptococcus ferus • Streptococcus iniae • Streptococcus intermedius • Streptococcus milleri group • Streptococcus mitior • Streptococcus mitis • Streptococcus mutans • Streptococcus oralis • Streptococcus parasanguinis • Streptococcus peroris • Streptococcus pneumoniae • Streptococcus pseudopneumoniae • Streptococcus pyogenes • Streptococcus ratti • Streptococcus salivarius • Streptococcus sanguinis • Streptococcus sobrinus • Streptococcus suis • Streptococcus thermophilus • Streptococcus uberis • Streptococcus vestibularis • Streptococcus viridans • Streptococcus zooepidemicus
Streptococcus (n.) [MeSH]
Classe des Asporulales (fr)[ClasseTaxo.]
eubacteria; eubacterium; true bacteria[ClasseHyper.]
Ordre des Microcoques (fr)[Classe]
bactérie pathogène pour l'homme (fr)[ClasseParExt.]
(quinsy; pharyngitis; sore throat; raw throat)[termes liés]
scarlatina, scarlet fever[Thème]
Streptococcus is a genus of spherical Gram-positive bacteria belonging to the phylum Firmicutes 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 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, and form part of the commensal human microbiome of the mouth, skin, intestine, and upper respiratory tract. Furthermore, streptococci are a necessary ingredient in producing Emmentaler ("Swiss") cheese.
Species of Streptococcus are classified based on their hemolytic properties. Alpha hemolytic species cause oxidization of iron in hemoglobin molecules within red blood cells, giving it a greenish color on blood agar. Beta hemolytic species cause complete rupture of red blood cells. On blood agar, this appears as wide areas clear of blood cells surrounding bacterial colonies. Gamma-hemolytic species cause no hemolysis.
Beta-hemolytic streptococci are further characterised via Lancefield serotyping, which describes specific carbohydrates present on the bacterial cell wall. There are 20 described serotypes, named Lancefield groups A to V (excluding I and J).
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”).
Inflammation is thought to be the major cause of how pneumococcus causes disease, hence the inflammatory nature of the diagnoses associated with it [ above ].
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.
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. 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. 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; 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.
This group includes S. equi, which causes strangles in horses, 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.
Many former Group D streptococci have been reclassified and placed in the genus Enterococcus (including Enterococcus faecalis, Enterococcus faecium, Enterococcus durans, and Enterococcus avium). For example, Streptococcus faecalis is now Enterococcus faecalis.
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 were first described in 1934 by Long and Bliss amongst the "minute haemolytic streptococci". 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).
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.