Group B streptococcus (GBS; Streptococcus agalactiae) is a gram-positive coccus that frequently colonizes the human genital and gastrointestinal tracts, and the upper respiratory tract in young infants [1,2]. It is an important cause of infection in three populations:
●Neonates — GBS infection is acquired in utero or during passage through the vagina. The most common manifestations of neonatal disease are bacteremia without a focus, sepsis, pneumonia, and/or meningitis. (See "Group B streptococcal infection in neonates and young infants".)
●Pregnant women — GBS is a frequent cause of urinary tract infection, chorioamnionitis, postpartum endometritis, and bacteremia in pregnant women. (See "Group B streptococcal infection in pregnant women".)
●Nonpregnant adults — GBS is increasingly recognized as a cause of bacteremia without a focus, sepsis, soft tissue infections, and other focal infections in nonpregnant adults.
GBS infection in nonpregnant adults will be reviewed here. The microbiology and epidemiology of infections caused by this organism and prevention strategies through chemoprophylaxis and vaccination are discussed separately. (See "Group B streptococcus: Virulence factors and pathogenic mechanisms" and "Neonatal group B streptococcal disease: Prevention" and "Vaccines for the prevention of group B streptococcal disease".)