Early-onset group B streptococcus neonatal disease: a target for prevention?

Group B streptococcus (GBS), or Streptococcus agalactiae, is a coloniser of the gastro-intestinal and urogenital tracts of humans and animals such as cattle. It has a worldwide distribution. Occasionally, it is implicated in human disease, such as urinary tract and soft tissue infections, and invasive disease especially in immunocompromised hosts.1 In pregnancy, the organism can lead to maternal chorioamnionitis, puerperal endometritis, and neonatal sepsis.2 Earlyonset (EO) neonatal disease, occurring within the first 7 days of life, is the most significant disease entity amenable to preventive measures. Late-onset disease occurs in infants 7 days or older. Determinants of late-onset disease are not well documented, although evidence suggests that it could be acquired through either vertical or nosocomial transmission, and that acquisition from community sources was also possible.3 Neonatal disease usually occurs as bacteraemia, pneumonia, or meningitis. Among the risk factors increasing the likelihood of EOGBS disease, the most important is GBS colonisation of the maternal urogenital or gastro-intestinal tract. Other risk factors include prolonged membrane rupture, intrapartum fever, less than 37 weeks’ gestation, GBS bacteriuria during pregnancy, and previous delivery of an infant who had GBS disease.3 Affected neonates usually acquire the bacteria during delivery via the ascending route. Early-onset GBS disease was previously associated with high mortality rates (up to 50%), but more recent estimates yield figures of less than 10%, probably due to improvements in neonatal care.3 Survivors may nevertheless suffer permanent disabilities, such as hearing or visual loss or mental retardation.