Group B Streptococcus (GBS or Streptococcus agalactiae) is an encapsulated gram-positive diplococcus that colonizes the gastrointestinal and genital tracts of 15 to 40 percent of pregnant women. GBS colonization is usually asymptomatic. However, maternal colonization is the primary risk factor for GBS infection in neonates and young infants (younger than 90 days of age) [1,2]. Vertical transmission generally occurs after the onset of labor or rupture of the fetal membranes .
GBS infection in neonates and young infants will be reviewed here. The microbiology of GBS infections, the prevention of GBS infection in neonates, and the management of infants whose mother received GBS chemoprophylaxis are discussed separately. (See "Group B streptococcus: Virulence factors and pathogenic mechanisms" and "Neonatal group B streptococcal disease: Prevention" and "Management of the infant whose mother has received group B streptococcal chemoprophylaxis".)
Group B streptococcal (GBS) infection in neonates and young infants is classified by age at onset .
Early-onset GBS — Early-onset GBS generally presents at or within 24 hours of birth , but can occur through day six of life.
Late-onset GBS — Late-onset GBS usually occurs at four to five weeks of age (range 7 to 89 days).