Streptococcus

Jump to: navigation, search
Streptococcus
Streptococcus.jpg
Scientific classification
Kingdom: Eubacteria
Phylum: Firmicutes
Class: Bacilli
Order: Lactobacillales
Family: Streptococcaceae
Genus: Streptococcus
Rosenbach, 1884
Species

S. agalactiae
S. bovis
S. mutans
S. pneumoniae
S. pyogenes
S. salivarius
S. sanguinis
S. suis
Streptococcus viridans
Streptococcus uberis
etc.

WikiDoc Resources for

Streptococcus

Articles

Most recent articles on Streptococcus

Most cited articles on Streptococcus

Review articles on Streptococcus

Articles on Streptococcus in N Eng J Med, Lancet, BMJ

Media

Powerpoint slides on Streptococcus

Images of Streptococcus

Photos of Streptococcus

Podcasts & MP3s on Streptococcus

Videos on Streptococcus

Evidence Based Medicine

Cochrane Collaboration on Streptococcus

Bandolier on Streptococcus

TRIP on Streptococcus

Clinical Trials

Ongoing Trials on Streptococcus at Clinical Trials.gov

Trial results on Streptococcus

Clinical Trials on Streptococcus at Google

Guidelines / Policies / Govt

US National Guidelines Clearinghouse on Streptococcus

NICE Guidance on Streptococcus

NHS PRODIGY Guidance

FDA on Streptococcus

CDC on Streptococcus

Books

Books on Streptococcus

News

Streptococcus in the news

Be alerted to news on Streptococcus

News trends on Streptococcus

Commentary

Blogs on Streptococcus

Definitions

Definitions of Streptococcus

Patient Resources / Community

Patient resources on Streptococcus

Discussion groups on Streptococcus

Patient Handouts on Streptococcus

Directions to Hospitals Treating Streptococcus

Risk calculators and risk factors for Streptococcus

Healthcare Provider Resources

Symptoms of Streptococcus

Causes & Risk Factors for Streptococcus

Diagnostic studies for Streptococcus

Treatment of Streptococcus

Continuing Medical Education (CME)

CME Programs on Streptococcus

International

Streptococcus en Espanol

Streptococcus en Francais

Business

Streptococcus in the Marketplace

Patents on Streptococcus

Experimental / Informatics

List of terms related to Streptococcus

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

Streptococcus is a genus of spherical Gram-positive bacteria, belonging to the phylum Firmicutes[1] 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 streptos, meaning easily bent or twisted, like a chain. Contrast this with staphylococci, which divide along multiple axes and generate grape-like clusters of cells.

Streptococci are oxidase– and catalase–negative.

Pathogenesis

In addition to 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 commensal flora 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 (breakdown of red blood cells in a laboratory).[2] 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 serotyping - based on specific carbohydrates in the bacterial cell wall.[3] 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

Viridans and Others

Beta-Hemolytic Streptococci

Group A

S. pyogenes (also known as GAS) is the causative agent in Group A streptococcal infections, (GAS) including 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 joints and heart valves. 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

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 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.[4] 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 Strep.[5]

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 [6] 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.[7]

Group C

Includes S. equi, which causes strangles in horses,[8] and 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. faciem, S. durans, and S. avium).[9] 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

  1. Ryan KJ; Ray CG (editors) (2004). Sherris Medical Microbiology, 4th ed., McGraw Hill. ISBN 0-8385-8529-9. 
  2. 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. 
  3. Facklam R (2002). "What happened to the streptococci: overview of taxonomic and nomenclature changes". Clin Microbiol Rev 15 (4): 613-30. PubMed.
  4. 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.
  5. Hughes, RG, et al.. "Prevention of Early Onset Neonatal Group B Streptococcal Disease" (HTML). Royal College of Obstetricians and Gynaecologists.
  6. Group B Strep Support Home Page (HTML). Group B Strep Support (2007-01-09).
  7. RCOG: Preventing group B streptococcus infection in new born babies (HTML). RCOG (2006-02).
  8. Harrington D, Sutcliffe I, Chanter N (2002). "The molecular basis of Streptococcus equi infection and disease". Microbes Infect 4 (4): 501-10. PMID 11932201.
  9. Ruoff KL (1990). "Recent taxonomic changes in the genus Enterococcus". Eur J Clin Microbiol Infect Dis 9 (2): 75-9. PMID 2108030.

External Links


Linked-in.jpg