n :  the Lancefield group of usu. beta-hemolytic streptococci that comprises all strains of a species of the genus Streptococcus (S. agalactiae) and that includes the causative agents of certain infections (as septicemia, pneumonia, and meningitis) esp. of newborn infants - often used attributively <affected with Group B strep>  - compare GROUP A  .
 
 
 
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