Strep Throat
Micr 201
Professor: Dr Hoch
Carrie Matthews
Joanne Nguyen
12/11/07
Taxonomy
• Super
Kingdom:
• Phylum:
• Class:
• Order:
• Family:
• Genus :
• Species:
Bacteria
Firmicutes
Bacilli
Lactobacillales
Streptococcaceae
Streptococcus
Streptococcus pyogenes
Streptococcus pyogenes Bacterium
• Group A Streptococcus.
• Nonmotile, non-sporeforming
coccus that occurs in chains or
in pairs of cells.
• Facultative anaerobe
• Requires enriched medium
with blood to grow.
• Capsule composed of
hyaluronic acid and exhibit
beta-hemolysis of blood agar.
• Causes an array of diseases.
Virulence Factors
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M protein
Protein F
Lipoteichoic acid
Hyaluronic acid capsule
Invasins (streptokinase, streptodornase, hyaluronidase, and
streptolysins)
• Exotoxins
• When host defenses are compromised, the organism is able to
exert its virulence and causes infection.
Target Tissues
• Throat and tonsils.
• Bacteria present in nose and
throat.
• Inflammatory process of the
oropharynx and or
nasopharynx.
Portals of Entry
• Upper respiratory tract or
skin.
Ecology
• Part of normal microbiota.
• Widely distributed in human; some become asymptomatic
carriers.
• Estimated that 5-15% of humans harbor it without signs of
disease.
Pathogenesis
• Multiply and spread rapidly in host while evading phagocytosis
and confusing the immune system.
Infection Process
• Spread by droplets of saliva or
nasal secretions.
• Stimulates inflammatory
response.
• Lysis of leukocytes and
erythrocytes.
• An inflammatory exudate
(cells and fluid) is released
from blood vessels and
deposited in surrounding
tissue.
Symptoms
• Symptoms observed in 1 to 3
days.
• Develop red throat with white
patches; red and enlarged
tonsils.
• Trouble swallowing.
• Tender, swollen lymph glands
on sides of neck.
• Fever (101˚F), pain, redness,
swelling of throat and tonsils.
• Headache
• Abdominal pain.
• Nausea
Diagnostic Tests
• Rapid Antigen Detection Assay
 Faster and more convenient.
 Less sensitivity.
• Throat swab culture
 High sensitivity.
 Requires 24-48 hours for results.
 Confirms a negative RADT.
Treatments
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Strep throat goes away after 3-7 days with or without treatment.
Doctors may prescribe an antibiotic
Penicillin is the drug of choice.
Erythromycin is the alternative.
70% of children are perscribed antibiotics; however, 30% have
strep infections; 50% had the cold or other viral infection.
Antibiotics treat bacterial infection, not viral infections.
Drink enough fluids.
Gargle with salt water.
Get extra sleep to promote a rapid recovery.
Preventative Measures
• Avoid contact with those infected
with strep throat.
• Wash hands frequently when
around those with colds; viral or
bacterial illnesses.
• Not sharing food or utensils with
others.
• Dispose used tissues properly.
Epidemiology
• Race- No racial or ethnic predisposition to infection or
complications is known.
• Sex- Both sexes are affected equally.
• Age- can affect persons of all ages, with a peak incidence in
children aged 5-15 years.
• In children, GAS accounts for approximately 30% of cases of
acute pharyngitis.
• The prevalence of GAS is significantly lower in adults,
accounting for only 5-10% of cases of pharyngitis.
Morbidity & Mortality
• Morbidity and mortality is extremely rare, but may be due to
other complications including:
– Post streptococcal sequlae: Rheumatic fever and Post
streptococcal glomerulonephritis (1-3% of untreated
infections).
– Less than .05% of Rheumatic fever is caused by
streptococcal infections.
– Localized purulent complications (otitis media, sinusitis,
peritonsillar and retropharyngeal abscess, and suppurative
cervical adenitis).
– Toxic shock syndrome mortality rate over 30%.
– GAS bacteremia mortality rate is 25-48%.
Latest Research
• Macrolide resistance in Streptococcal pharyngitis:
 Studies in 2007 found that 42.6% of isolates were resistant to
erythromycin; 39.6% to clindamycin.
• In 1997, erythromycin was considered the drug alternative.
 Dirithromycin (new macrolide) is an alternative to penicillin for patients
12 years of age and older.
• Study done between Jan. 1, 1996 – Dec. 31, 1998 involving 208
children (ages 4-15) who had 3/more GABHS pharyngitis
episodes in one yr for at least one month apart.
• Study to test diagnostic value of rapid antigen test.
• Study done comparing RADT and Throat swab culture.
References
A H Abu-Sabaah, H O Ghazi. British Journal of Biomedical Science. London: 2006. Vol. 63, Iss. 4; pg. 155, 4 pgs.
Antimmicrob. Agents Chemother. 1997 41: 72-75. www.journals.asm.org.
Center for Disease Control, Division of Bacterial and Mycotic Diseases. 2005. “Group A Streptococcal (GAS) Disease”.
http://www.cdc.gov/ncidod/dbmd/diseaseinfo/groupastreptococcal_g.htm.
Florence Paillard, Craig S Hill, Ronald A Blum, Linda Dearing. Medical Laboratory Observer. Montvale: Jan 2004. Vol. 36, Isss. 1; p. 10.
Jennifer L St Sauver, Amy L Weaver, Laura J Orvidas, Robert M Jacobson, Steven J Jacobsen. Mayoclinic Proceedings. Rochester: Sep 2006. Vol 81,
Iss. 9; pg. 1172, 5 pgs.
Joanne M. Willey, Linda M. Sherwood, Christopher J. Woolverton. Microbiology. Seventh Edition. New York: McGraw-Hill, 2008.
National Institute of Allery and Infection Diseases. “Group A Streptococcal Infections”. 9 Dec 2007. 19 Sept 2007.
http://www3.niaid.nih.gov/healthscience/healthtopics/streptococcal/overview.htm.
Shuford, Gordon. “Common items carry strep threat”. 5 Dec 2007.
http://images.google.com/imgres?imgurl=http://www.jour.sc.edu/pages/wigginsweb/faucet.jpg&imgrefurl=http://www.jour.sc.edu/pages/wigginswe
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Todar, Ken. 2002. “Streptococcus pyogenes”. 5 Dec 2007. “Streptococcus pyogenes” http://textbookofbacteriology.net/streptococcus.html.
Web MD. “Strep Throat”. 5 Dec 2007. http://www.webmd.com/a-to-z-guides/strep-throat-prevention.
WebMD. “Strep Throat”. 2003-2007. 30 Nov 2007. http://www.emedicinehealth.com/strep_throat/page6_em.htm.
Valery Lavergne, Louise Thibault, Richard Garceau. Canadian Medical Association. Journal. Ottawa: Jul 17, 2007. Vol. 177, Iss. 2; p. 177.