Group A streptococcus (Streptococcus pyogenes) is responsible for 5 to 15% of cases of pharyngitis in adults and 20 to 30% of cases in children
Common northern regions esp. during winter/early spring
Affects children/young adults
More than 10 million noninvasive GAS infections (primarily throat and superficial skin infections) occur annually.
streptococci are gram positive, catalase-negative cocci in pairs
S pyogenes tends to colonize the upper respiratory tract and is highly virulent as it overcomes the host defense system
The outermost capsule is composed of hyaluronic acid, which has a chemical structure resembling host connective tissue, allowing the bacterium to escape recognition by the host as an offending agent. Thus, the bacterium escapes phagocytosis by neutrophils or macrophages, allowing it to colonize
10-day course of penicillin V 250 mg twice daily in children
500 mg twice daily or 250 mg 4 times daily in adults
A single intramuscular injection of 1.2 million units of penicillin G benzathine can be administered in patients who weigh more than 27 kg; 600,000 units is used in patients who weigh less than 27 kg.
Amoxicillin is equally effective and may be better tolerated in children.
In patients who are allergic to penicillin, erythromycin or the newer macrolides (eg, azithromycin, clarithromycin) appear to be effective. Oral cephalosporins are also highly effective in the treatment of streptococcal pharyngitis.