Neonatal meningitis is most often caused by which pathogens, and what is the recommended empiric regimen?

• A. Haemophilus influenzae type b and Neisseria meningitidis; ceftriaxone
• B. Pseudomonas aeruginosa and Klebsiella; piperacillin-tazobactam
• C. Staphylococcus aureus and Listeria monocytogenes; vancomycin
• D. Group B Streptococcus and Escherichia coli; ampicillin plus gentamicin

Answer: (D)

Neonatal meningitis is driven by organisms that newborns are exposed to around birth, with the two most common culprits being Group B Streptococcus and Escherichia coli. The aim of empiric therapy is to cover both the Gram-positive organism that commonly colonizes the maternal genital tract and the Gram-negative rods that can cause serious infection in newborns, including organisms like E. coli. Ampicillin is used to cover Group B Streptococcus and also provides some protection against Listeria monocytogenes, while adding an aminoglycoside such as gentamicin targets Gram-negative bacteria, including E. coli. This combination thus offers broad initial coverage appropriate for suspected neonatal meningitis. Other regimens miss one of the key targets or rely on drugs with safety or CNS-penetration concerns in neonates (for example, agents that aren’t ideal for Listeria coverage, or choices avoided in newborns), making them less suitable as empiric therapy.