Definition
A group A streptococcal infection includes contagious illnesses caused by the bacterium Streptococcus pyogenes. The most common group A infection is strep throat. Other group A infections include impetigo (superficial skin infection) and serious deep tissue and blood infections. In rare cases, infection with group A strep can result in complications such as rheumatic fever and post-strep glomerulonephritis (kidney inflammation).
Causes
S. pyogenes bacteria are commonly found in the throat and on
skin. During peak times between fall and spring, up to 20 percent of school-age
children may carry the bacteria and may transmit it without becoming ill. The
organism is spread person to person through respiratory droplets or through direct
contact. Infected persons are contagious as long as they have symptoms. Infections
that go untreated with antibiotics may be contagious beyond
the symptomatic period.
While most cases of pharyngitis (strep throat) are viral, group A strep is the most common bacterial cause. Virulence factors of the bacterial cell influence the severity of the disease.
Risk Factors
Factors that increase the risk of developing localized group A strep infection, including strep throat and impetigo, are age (children of all ages), time of year (between fall and spring), and exposure to school-age children. Having a past history of group A strep infection may predispose one to future infection.
The risk of more severe invasive disease is increased by chickenpox
infection, other infections of the skin, and immunosuppression of any cause.
Infection with group A strep carries a risk of complications that include
rheumatic fever and post-strep glomerulonephritis.
Symptoms
Symptoms of strep throat include fever, sore throat, and swollen lymph nodes, sometimes accompanied by headache and vomiting. Redness, swelling, and pus may be present on the tonsils.
Symptoms of infection elsewhere depend on the area of the body, but usually
include redness, inflammation, and swelling accompanied by fever. Symptoms of
bacteremia (bacterial blood infection) often include fever
and shaking chills.
Screening and Diagnosis
Diagnosis of strep throat may be made by laboratory test (rapid antigen test or throat culture) but often is made clinically if the signs and symptoms point to infection. The absence of typical viral symptoms, such as runny nose and cough, may indicate strep.
Group A strep infection is suspected when redness, inflammation, and swelling are present in an area that is a common location for that type of infection. A blood culture is required for diagnosis of strep bacteremia. Occasionally, a diagnosis is made following the appearance of one of the complications of strep infection, such as post-strep glomerulonephritis.
Treatment and Therapy
When a diagnosis of strep infection is confirmed or strongly suspected,
antibiotic treatment is indicated to shorten the duration of symptoms, to shorten
the time of contagiousness, and to prevent complications. Penicillin is
effective when administered orally or by injection. Other antibiotics are used for
persons allergic to penicillin.
Prevention and Outcomes
Prevention involves minimizing the spread of bacteria. Frequent handwashing, careful personal hygiene, and avoiding the respiratory secretions of others help to prevent transmission.
Bibliography
Gerber, M. “ Streptococcus pyogenes (Group A Streptococcus).” In Principles and Practice of Pediatric Infectious Diseases, edited by Sarah S. Long, Larry K. Pickering, and Charles G. Prober. 3d ed. Philadelphia: Churchill Livingstone/Elsevier, 2008.
Hahn, R. G., et al. “Evaluation of Poststreptococcal Illness.” American Family Physician 71 (2005): 1949-1954.
Jaggi, P., and S. T. Shulman. “Group A Streptococcal Infections.” Pediatrics in Review 27 (2006): 99-104.
Khan, Zartash Zafar, et al. “Streptococcus Group A Infections.” Available at http://emedicine.medscape.com/article/228936-overview.
Landau, Elaine. Strep Throat: Head-to-Toe Health. Tarrytown, N.Y.: Benchmark Books, 2010.
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