Strep throat causes
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Aysha Anwar, M.B.B.S[2]
Overview
Strep throat is caused by B hemolytic Group A streptococcal infection. More than 80 serotypes are identified based on M protien. GAS strep throat may be associated with serotypes such as M types 1, 3, 5, 6, 14, 18, 19, and 24.[1]
Causes
Strep throat is caused by B hemolytic Group A streptococcal infection.
Reservoir
- Members of the normal flora
- Human skin and mucous membrane are the only known reservoirs
Serovars
- More than 80 serotypes identified based on M protien
- GAS strep throat may be associated with serotypes such as M types 1, 3, 5, 6, 14, 18, 19, and 24.[1][2][3]
Features of group A streptococcal infection
- Gram-positive coccus (grows in chains)
- Non-motile
- Non-spore forming
- 0.5-1.2µm in size
- Catalase-negative
- Facultative anaerobes or obligate (strict) anaerobes
- Requires enriched media (blood agar) to grow
- Capsulated (hyaluronic acid capsule)
Classification of GAS
- According to the Lancefield classification, based on the group A antigen in the cell wall, it is named group A streptococcus
- Based on the hemolysis on blood agar, the GAS is β-hemolytic (clear, complete lysis of red cells)
Virulence factors
Virulence factors of group A streptococci include:[4][5]
- A hyaluronic acid capsule (outermost covering inhibits phagocytosis)
- Peptidoglycan cell wall
- Cell membrane
- Adhesion molecules
- M protein PMC358122
- Lipoteichoic acid (located in cell membrane)
- Pyrogenic (erythrogenic) toxin (rash of scarlet fever)
- Streptokinase
- Streptodornase (DNase B)
- Streptolysins
- Hyaluronidase
References
- ↑ 1.0 1.1 Fischetti VA (1989). "Streptococcal M protein: molecular design and biological behavior". Clin Microbiol Rev. 2 (3): 285–314. PMC 358122. PMID 2670192.
- ↑ Cunningham MW (2000). "Pathogenesis of group A streptococcal infections". Clin Microbiol Rev. 13 (3): 470–511. PMC 88944. PMID 10885988.
- ↑ Stanley J, Desai M, Xerry J, Tanna A, Efstratiou A, George R (1996). "High-resolution genotyping elucidates the epidemiology of group A streptococcus outbreaks". J Infect Dis. 174 (3): 500–6. PMID 8769606.
- ↑ Smeesters PR, McMillan DJ, Sriprakash KS (2010). "The streptococcal M protein: a highly versatile molecule". Trends Microbiol. 18 (6): 275–82. doi:10.1016/j.tim.2010.02.007. PMID 20347595.
- ↑ Mora M, Bensi G, Capo S, Falugi F, Zingaretti C, Manetti AG; et al. (2005). "Group A Streptococcus produce pilus-like structures containing protective antigens and Lancefield T antigens". Proc Natl Acad Sci U S A. 102 (43): 15641–6. doi:10.1073/pnas.0507808102. PMC 1253647. PMID 16223875.