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Treatment and Future Directions
Because S. pyogenes is a bacteria, the common treatment for an infection is an antibiotic. Fortunately, S. pyogenes is almost universally susceptible to penicillin (Todar 2002). Erythromycin is also a common treatment for streptococcal infections, especially for those allergic to penicillin. However, resistance to erythromycin is increasing. Over a five year period, streptococcal strains in Genoa went from being completely susceptible to having a 50% resistance rate, and erythromycin-resistant GAS have been observed in many countries, including the United States (Bassetti 2000).
Once an individual clears a GAS infection, there can be long term complications. Some individuals develop rheumatic fever after a strep throat infection; however, this occurs in less than 1% of cases (Todar 2002). Rheumatic fever occurs when antibodies produced to fight off S. pyogenes also bind to the host heart cells (Todar 2002; Zabriskie 1983). The mechanism behind rheumatic fever was first elucidated in the 1960s when researchers used immunofluorescence to show that some mouse anti-streptococci antibodies also bound to human myocardial cells. The researchers then found similar antibodies in individuals affected with rheumatic fever. Cytotoxic lymphocytes specific for cardiac cells were later discovered in some rheumatic fever patients (Zabriskie 1983). For young people throughout the world, rheumatic fever is one of the leading causes of acquired heart disease (Center 2005).
Vaccine research against S. pyogenes, specifically the M protein, has been limited due to the variability of the M protein and the increased risk of autoimmune problems, such as rheumatic fever. However, now that the M protein has been sequenced and different cross-reactive epitopes have been characterized, researchers are one step closer to creating a vaccine for certain S. pyogenes strains. However, much more work must be done before a vaccine reaches the market (Todar 2002).
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