ABSTRACT
The group B beta-hemolytic streptococcus (Streptococcus agalactiae) is a gram-positive coccus that grows in chains in vitro and in vivo. On appropriate media, the colonies appear as smooth, shiny white mounds, about 1 to 1.5 mm in diameter, with a narrow zone of beta-hemolysis. The group B streptococcus (GBS) lacks the M protein that is characteristic of the group A organisms; consequently, its virulence and pathogenicity for humans differ markedly from those of Streptococcus pyogenes.
