Which organism is the leading cause of meningitis in neonates?

• A. Escherichia coli
• B. Listeria monocytogenes
• C. Streptococcus agalactiae
• D. Streptococcus pneumoniae

Answer: (C)

Group B Streptococcus (Streptococcus agalactiae) is the leading cause of meningitis in newborns because many pregnant women carry it in the vaginal or rectal tract and it can be transmitted to the infant during birth, seeding the bloodstream and meninges. The organism’s capsule helps it resist phagocytosis, enabling invasive disease in the newborn. This often presents as early-onset disease within the first week of life, with meningitis being a common manifestation. Preventive measures include screening pregnant women for GBS colonization and giving intrapartum antibiotics to carriers or those with unknown status, which has substantially reduced neonatal disease. While other pathogens like E. coli, Listeria monocytogenes, and Streptococcus pneumoniae can cause neonatal meningitis, Group B Streptococcus remains the most frequent culprit in this age group.