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A group A streptococcal infection is an infection with group A streptococcus (GAS), that is, ''Streptococcus pyogenes'', the sole species constituting Lancefield group A. This beta-hemolytic species of bacteria is responsible for a wide range of both invasive and noninvasive infections.〔(【引用サイトリンク】url=http://www.cdc.gov/ncidod/dbmd/diseaseinfo/groupastreptococcal_g.htm )〕 Infection of GAS may spread through direct contact with mucus or sores on the skin.〔 GAS infections can cause >500,000 deaths per year. Despite the emergence of antibiotics as a treatment for group A β-hemolytic streptococcus, infection of GAS is an increasing problem, particularly in the continent of Africa. There are many other types of streptococci (species of ''Streptococcus''), including group B streptococcus (''Streptococcus agalactiae'') and ''Streptococcus pneumoniae'', which cause other types of infections and should not be confused with group A strep. Several virulence factors contribute to the pathogenesis of GAS, such as M protein, hemolysins, and extracellular enzymes. ==Types of infection== Group A β-hemolytic streptococcus may cause an infection to the throat and skin.〔(【引用サイトリンク】publisher=Centers for Disease Control and Prevention )〕 These may vary from very mild conditions to severe, life-threatening diseases. Although it is not completely clear what causes different people to develop different diseases as a result of the same pathogenic bacteria, it is suspected that certain people have certain genes turned on and certain genes turned off, resulting in various diseases. These switches can be controlled by the many virulence factors of GAS. Also, persons with suppressed or compromised immune systems may be more susceptible to certain diseases caused by GAS than other persons with stronger immune systems. People may also carry the GAS either on the skin or in the throat and show no symptoms.〔(【引用サイトリンク】url=http://www.nyc.gov/html/doh/html/cd/cdstrep.shtml )〕 These carriers are less contagious than symptomatic carriers of the bacteria.〔 The non-invasive infections caused by GAS tend to be less severe and more common. They occur when the bacteria colonizes in the throat area, where it recognizes epithelial cells.〔(【引用サイトリンク】url=http://www.medicinenet.com/streptococcal_infections/page2.htm )〕 The two most prominent infections of GAS are both non-invasive: strep throat (pharyngitis) where it causes 15- 30% of the childhood cases and 10% of adult cases, and impetigo.〔 These may be effectively treated with antibiotics. Scarlet fever is also a non-invasive infection caused by GAS, although much less common. The invasive infections caused by Group A β-hemolytic streptococcus tend to be more severe and less common. This occurs when the bacterium is able to infect areas where bacteria are not usually found, such as blood and organs.〔 The diseases that may be caused as a result of this include streptococcal toxic shock syndrome (STSS), necrotizing fasciitis (NF), pneumonia, and bacteremia.〔 In addition, infection of GAS may lead to further complications and health conditions, namely acute rheumatic fever and poststreptococcal glomerulonephritis. Most Common: * impetigo, cellulitis, and erysipelas – infections of the skin which can be complicated by necrotizing fasciitis – skin, fascia and muscle * strep throat AKA strep pharyngitis – pharynx Less Common: * Bacteremia can be associated with these infections, but is not typical. * septic arthritis – joints * osteomyelitis – bones * vaginitis – vagina (more common in pre-pubescent girls) * meningitis * – meninges * sinusitis * – sinuses * pneumonia * – pulmonary alveolus ( *Note that meningitis, sinusitis and pneumonia can all be caused by Group A Strep, but are ''much'' more commonly associated with Streptococcus pneumoniae and should not be confused.) Complications of Group A Strep: * toxic shock syndrome * scarlet fever * Rheumatic fever * Post-streptococcal glomerulonephritis * PANDAS ==Complications== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Group A streptococcal infection」の詳細全文を読む スポンサード リンク
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