Streptococcus

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Streptococcus

Streptococcus is a genus

Genus

A genus is a low-level taxonomic rank used in the classification of living and fossil organisms. The taxonomic ranks are domain , kingdom , phylum, class , order , family , genus, and species....
of spherical

Sphere

A sphere is a symmetrical geometrical object. In non-mathematical usage, the term is used to refer either to a round ball or to its two-dimensional surface....
Gram-positive

Gram-positive

Gram-positive Bacteria are those that are stained dark blue or violet by Gram staining. This is in contrast to Gram-negative bacteria, which cannot retain the crystal violet stain, instead taking up the counterstain and appearing red or pink....
bacteria belonging to the phylum Firmicutes

Firmicutes

The Firmicutes are a division of bacterium, most of which have Gram-positive cell wall structure. A few, the Mollicutes or mycoplasmas, lack cell walls altogether and so do not respond to Gram staining, but still lack the second membrane found in other Gram-negative forms....
and the lactic acid bacteria

Lactic acid bacteria

The Lactic Acid Bacteria comprise a clade of Gram-positive, low-GuanineCytosine, acid-tolerant, generally non-sporulating, non-respiring rod or cocci that are associated by their common metabolic and physiological characteristics....
group. Cellular division

Cell division

Cell division is a process by which a cell , called the parent cell, divides into two or more cells, called daughter cells. Cell division is usually a small segment of a larger cell cycle....
occurs along a single axis in these bacteria, and thus they grow in chains or pairs, hence the name — from Greek

Greek language

Greek is an Indo-European languages native to the southern Balkan peninsula, the language of the Greek people. It forms an independent branch within Indo-European....
st?ept?? streptos, meaning easily bent or twisted, like a chain (twisted chain). Contrast this with staphylococci

Staphylococcus

Staphylococcus is a genus of Gram-positive Bacterium. Under the microscope they appear round , and form in grape-like clusters.The Staphylococcus genus include just thirty-three species....
, which divide along multiple axes and generate grape-like clusters of cell

Cell (biology)

The cell is the structural and functional unit of all known Life organisms. It is the smallest unit of an organism that is classified as living, and is often called the building bricks of life....
s.

Streptococci are oxidase

Oxidase

An oxidase is any enzyme that catalyst an redox reaction involving molecular oxygen as the electron acceptor. In these reactions, oxygen is reduced to water or hydrogen peroxide ....
- and catalase

Catalase

Catalase is a common enzyme found in nearly all living organisms which are exposed to oxygen, where it functions to catalyst the decomposition of hydrogen peroxide to water and oxygen....
-negative.

In 1984, many organisms formerly considered Streptococcus were separated out into Enterococci and Lactococci.

Morphology: Streptococci are Gram positive more or less spherical sometimes ovoid.

ddition to strep throat, certain Streptococcus species are responsible for many cases of meningitis

Meningitis

Meningitis is a medical condition caused by inflammation of the protective membranes covering the brain and spinal cord, known collectively as the meninges....
, bacterial pneumonia

Bacterial pneumonia

Bacterial pneumonia is a type of pneumonia associated with bacterial infection....
, endocarditis

Endocarditis

Endocarditis is an inflammation of the inner layer of the heart, the endocardium. It usually involves the heart valves . Other structures which may be involved include the interventricular septum, the chordae tendinae, the mural endocardium, or even on intracardiac devices....
, erysipelas

Erysipelas

Erysipelas is an acute streptococcus bacterial infection of the dermis, resulting in inflammation and characteristically extending into underlying fat tissue....
and necrotizing fasciitis

Necrotizing fasciitis

Necrotizing fasciitis , commonly known as flesh-eating disease or flesh-eating bacteria, is a Rare disease infection of the deeper layers of skin and Subcutiss, easily spreading across the fascial plane within the subcutaneous tissue....
(the 'flesh-eating' bacterial infections).

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Pathogenesis

In addition to strep throat, certain Streptococcus species are responsible for many cases of meningitis

Meningitis

Meningitis is a medical condition caused by inflammation of the protective membranes covering the brain and spinal cord, known collectively as the meninges....
, bacterial pneumonia

Bacterial pneumonia

Bacterial pneumonia is a type of pneumonia associated with bacterial infection....
, endocarditis

Endocarditis

Erysipelas

Erysipelas is an acute streptococcus bacterial infection of the dermis, resulting in inflammation and characteristically extending into underlying fat tissue....
and necrotizing fasciitis

Necrotizing fasciitis

Commensalism

In ecology, commensalism is a class of relationship between two organisms where one benefits and the other is not significantly harmed or benefited....
flora

Flora (microbiology)

In microbiology, flora refers to the collective bacteria and other microorganisms in an ecosystem ....
of the mouth, skin, intestine, and upper respiratory tract of humans.

As a rule, individual species of Streptococcus are classified based on their hemolytic

Hemolysis (microbiology)

Hemolysis is the breakdown of red blood cells. The ability of bacterial colonies to induce hemolysis when grown on blood agar is used to classify certain microorganisms....
properties. 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 Lancefield

Rebecca Lancefield

Rebecca Craighill Lancefield was a prominent United States microbiologist. She joined the Rockefeller University in New York in 1918 and was associated to that institute throughout her long and outstanding career....
serotyping

Serovar

A serovar or serotype is a group of microorganisms or viruses classified together based on their cell surface antigens. Serovars allow the epidemiologic classification of organisms to the sub-species level....
– based on specific carbohydrates in the bacterial cell wall. These are named Lancefield groups A to T, although some species, such as S. pneumoniae, do not express Lancefield antigens. 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 streptococci

Pneumococci

S. pneumoniae
Streptococcus pneumoniae

Streptococcus pneumoniae, or pneumococcus, is a Gram-positive, Hemolysis diplococcus aerotolerant anaerobe and a member of the genus Streptococcus....
, a leading cause of bacterial pneumonia
Pneumonia

Pneumonia is an Inflammation illness of the lung. Frequently, it is described as lung parenchyma/alveolus inflammation and abnormal alveolar filling with fluid ....
, otitis media and meningitis
Meningitis

Meningitis is a medical condition caused by inflammation of the protective membranes covering the brain and spinal cord, known collectively as the meninges....
.

Viridans and others

S. mutans
Streptococcus mutans

Streptococcus mutans is a Gram-positive, Facultative anaerobic organism bacteria commonly found in the human oral cavity and is a significant contributor to dental caries....
, a contributor to dental caries
Dental caries

Dental caries, also known as tooth decay, is a disease where bacterial processes damage hard tooth structure . These tissues progressively break down, producing dental cavities ....
S. mitis
Streptococcus mitis

Streptococcus mitis is a mesophilic alpha-haemolytic species of Streptococcus that inhabits the human mouth. It can cause endocarditis. It has been widely reported that this organism survived for over two years on the Surveyor 3 probe on the moon....
, mostly found around cheek region
S. sanguinis
Streptococcus sanguinis

Streptococcus sanguinis, formerly known as Streptococcus sanguis, is a Gram-positive facultative coccus species of bacteria. S. sanguinis is a normal inhabitant of the healthy human mouth where it is particularly found in dental plaque, where it modifies the environment to make it less hospitable for other strains of Strepto...
, no preference of locations
S. salivarius
Streptococcus salivarius

Streptococcus salivarius is a species of sphere, Gram-positive bacterium which colonize the mouth and upper respiratory tract of humans a few hours after birth, making further exposure to the bacteria harmless....
, mostly found on the dorsal side of the tongue
S. viridans
Streptococcus viridans

Streptococcus viridans is a pseudo-taxonomic term for a large group of generally non-pathogenic, commensal Streptococcus bacteria that are either Hemolysis , producing a green coloration on blood agar plates , or non-hemolytic....
, a cause of endocarditis
Endocarditis

Endocarditis is an inflammation of the inner layer of the heart, the endocardium. It usually involves the heart valves . Other structures which may be involved include the interventricular septum, the chordae tendinae, the mural endocardium, or even on intracardiac devices....
and dental abscesses
Tooth abscess

A tooth abscess or root abscess is pus enclosed in the tissues of the jaw bone at the tip of an infected tooth. Usually the abscess originates from a bacterial infection that has accumulated in the soft pulp of the tooth....
S. salivarius ssp. thermophilus
Streptococcus thermophilus

Streptococcus salivarius subsp. thermophilus is a Gram-positive Facultative anaerobic organism. It is a cytochrome-, oxidase- and catalase-negative organism that is nonmotile, non-spore forming and homofermentative....
, used in the manufacture of some cheeses and yogurts
S. constellatus, occasional human pathogen, notable as colonies grown on blood agar
Agar

Agar or agar agar is a gelatinous substance derived from seaweed. Historically and in a modern context, it is chiefly used as an ingredient in desserts throughout Japan, but in the past century has found extensive use as a solid substrate to contain Growth medium for microbiology work....
smell strongly of caramel

Beta-hemolytic streptococci

Group A

S. pyogenes
Streptococcus pyogenes

'Streptococcus pyogenes' is a coccus gram-positive bacteria that grows in long chains and is the cause of Group A streptococcal infections. S....
, also known as Group A Streptococcus (GAS), is the causative agent in Group A streptococcal infection

Group A streptococcal infection

The group A streptococcus bacterium is a form of Streptococcus bacteria responsible for most cases of streptococcal illness. Other types may also cause infection....
s, including streptococcal pharyngitis ("strep throat"), acute rheumatic fever

Rheumatic fever

Rheumatic fever is an inflammatory disease disease which may develop two to three weeks after a Group A streptococcal infection . It is believed to be caused by antibody cross-reactivity and can involve the heart, joints, skin, and brain....
, scarlet fever

Scarlet fever

Scarlet fever is a disease caused by an exotoxin released by Streptococcus pyogenes. The term Scarlatina may be used interchangeably with Scarlet Fever, though it is commonly used to indicate the less acute form of Scarlet Fever that is often seen since the beginning of the twentieth century....
, acute glomerulonephritis

Glomerulonephritis

Glomerulonephritis, also known as glomerular nephritis, abbreviated GN, is a kidney disease characterized by inflammation of the glomerulus, or small blood vessels in the kidneys....
and necrotizing fasciitis

Necrotizing fasciitis

Rheumatic fever

Joint

A joint is the location at which two or more bones make contact. They are constructed to allow movement and provide mechanical support, and are classified structurally and functionally....
s and heart valve

Heart valve

In anatomy, the heart valves maintain the unidirectional flow of blood in the heart by opening and closing depending on the difference in pressure on each side....
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

Rapid Strep Test

A Rapid Strep test or Rapid antigen detection test or RADT, is an in-office test done by a clinician determine whether or not a person has Strep throat caused by the organism beta-hemolytic Streptococcus pyogenes....
or by culture.

Group B

S. agalactiae
Streptococcus agalactiae

Streptococcus agalactiae is a beta-hemolytic gram-positive streptococcus....
, or GBS, causes pneumonia

Pneumonia

Pneumonia is an Inflammation illness of the lung. Frequently, it is described as lung parenchyma/alveolus inflammation and abnormal alveolar filling with fluid ....
and meningitis

Meningitis

Meningitis is a medical condition caused by inflammation of the protective membranes covering the brain and spinal cord, known collectively as the meninges....
in neonates and the elderly, with occasional systemic bacteremia

Bacteremia

Bacteraemia is the presence of bacterium in the blood. The blood is normally a sterile environment, so the detection of bacteria in the blood is always abnormal....
. 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. In the UK

United Kingdom

The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom , the UK or Britain,is a sovereign state located off the northwestern coast of continental Europe....
, clinicians have been slow to implement the same standards as the US, Australia

Australia

Australia, officially the Commonwealth of Australia, is a country in the southern hemisphere comprising the Australia of the world's smallest continent, the major island of Tasmania, and numerous list of islands of Australia in the Indian Ocean and Pacific Oceans....
and Canada

Canada

Canada is a country occupying most of northern North America, extending from the Atlantic Ocean in the east to the Pacific Ocean in the west and northward into the Arctic Ocean....
. In the UK, only 1% of maternity units test for the presence of Group B Strep. 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 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.

Group C

Includes S. equi, which causes strangles

Strangles

Strangles is a Disease#Transmission of disease, upper respiratory tract infection of horses and other equidae caused by a bacterium, Streptococcus equi var equi....
in horses, and S. zooepidemicus, which causes infections in several species of mammals including cattle and horses. This can also cause death in chickens and moose

Moose

File:Alces alces NA.svgThe moose or elk , , is the largest Extant taxon species in the deer family . Moose are distinguished by the palmate antlers of the males; other members of the family have antlers with a "twig-like" configuration....
.

Group D (enterococci) *variable in hemolysis

Many former Group D Streptococci have been reclassified and placed in the genus Enterococcus
Enterococcus

Enterococcus is a genus of lactic acid bacteria of the Phylum Firmicutes. Members of this genus were classified as Group D Streptococcus until 1984 when genomic DNA analysis indicated that a separate genus classification would be appropriate....
(including S. faecalis, S. faecium, S. durans, and S. avium). For example, Streptococcus faecalis is now Enterococcus faecalis
Enterococcus faecalis

Enterococcus faecalis ? formerly classified as part of the Group D Streptococcus system ? is a Gram-positive commensal bacterium inhabiting the gastrointestinal tracts of humans and other mammals....
.

The remaining non-enterococcal Group D strains include Streptococcus bovis
Streptococcus bovis

Streptococcus bovis is a catalase- and oxidase-negative, non-motile, non-endospore, Gram-positive lactic acid bacterium that grows as pairs or chains of cocci....
and Streptococcus equinus.

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.

Non-hemolytic streptococci

Non-hemolytic streptococci rarely cause disease. However, weakly hemolytic group D beta-hemolytic streptococci and Listeria monocytogenes
Listeria monocytogenes

Listeria monocytogenes, one of the most virulent foodborne pathogens with 20 percent of clinical infections resulting in death, is the causative agent of Listeriosis....
should not be confused with non-hemolytic streptococci.

External links

August 16, 2002 MMWR 2000;49:228-232.