Strep Throat

Micr 201Professor: Dr HochCarrie MatthewsJoanne Nguyen

12/11/07

Taxonomy

• Super Kingdom: Bacteria

• Phylum: Firmicutes• Class:Bacilli• Order: Lactobacillales• Family: Streptococcaceae • Genus : Streptococcus• Species: 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

• 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 AssayFaster and more convenient.Less sensitivity.

• Throat swab cultureHigh sensitivity.Requires 24-48 hours for results.Confirms a negative RADT.

Treatments

• 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.

ReferencesA 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/wigginsweb/strep.html&h=225&w=300&sz=8&hl=en&start=7&tbnid=doXU2QfY2fp9fM:&tbnh=87&tbnw=116&prev=.

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.