Group B streptococci colonize the nasopharynx, digestive tract and vagina. Most isolators are identified as S. agalactiae. Despite the fact that the microorganism can be isolated from the vagina with 25-45% pregnant women, the main reservoir is considered to be the digestive tract. In terms of serology, group B streptococci can be divided into serovars Ia, Ib, Ic, II and III. Serovar bacteria are trophic to the tissue of the central nervous system and respiratory tract and most often cause meningitis with neonates. The way of contamination is the advancing of the fetus through the generative passage infected by streptococci.