Medical Definition of Group A
: the Lancefield group of beta-hemolytic streptococci that comprises all strains of a species of the genus Streptococcus (S. pyogenes) and that includes the causative agents of pharyngitis, scarlet fever, septicemia, some skin infections (as pyoderma and erysipelas), rheumatic fever, and glomerulonephritis—usually used attributively <Group A streptococcal infections>; compare group b
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Dictionary: Definition of "Group A"
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