Review of group B streptococci and their infections

This review article discusses the stages in the development of research on group B streptococcus (GBS), otherwise called Streptococcus agalactiae. Emphasis was placed on the bacteriology, clinical spectrum of disease, immunity to GBS infections and antibiotic susceptibility of the causative organism. The organism, first recognized by Billroth in 1873, is classified into order Eubacteriales, family Lactobacillceae, class Schizomycetes and genus Streptococcus on the basis of its biochemical and physiological characteristics. It is subdivided into types Ia, Ib, Ic, II, III, X and R on the basis of carbohydrate and protein antigens present on its cell wall. Bovine strains of GBS are found in the bovine teat while human strains are present in the female vagina, the oro-pharynx, anorectum and the external auditory canal of newborns. It could be transmitted vertically from mother to child in-utero and during parturition. Cross infection by the nursery staff could also occur during the immediate post partum period. Two types of diseases are caused in the newborn: the early disease occurring within a week of birth; and the late disease presenting during the late neonatal period. The former usually presents in the form of septicaemia while the latter presents as meningitis. Adult infections include puerperal sepsis, pyelonephritis and a wide range of other infections. Usually they are associated with other underlying clinical conditions such as malignancy, diabetes mellitus and sickle cell disease. The organism is sensitive to penicillin which is the drug choice in treating established infections by GBS. Control measures are based on treatment of cases, eradication of vaginal colonization and chemoprophylaxis of infants at risk. An effective vaccine may become available in the near future.