The most common cause of neonatal sepsis in rich countries is group B streptococcus (Streptococcus agalactiae). It usually affects infants in the first three months of life, with vertical transmission from the mother being the cause in early onset disease (age 0–6 days) and maternally or environmentally acquired infection in late onset disease (age 7–89 days). Intrapartum antibiotic prophylaxis for high risk or known carrier mothers reduces the risk to the infants …