noun
Usage: usually capitalized G&A, often attributive
: the Lancefield group of 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
Group A streptococcal infections
— compare group b herein