Neonatal Meningitis Antibiotic Coverage
A 5-day-old female infant born at term presents with lethargy, poor feeding, and a temperature of 38.5 °C. The anterior fontanelle is full. Lumbar puncture shows 850 leukocytes per microlitre with 85 percent neutrophils, glucose 1.2 mmol/L against a blood glucose of 5.0 mmol/L, and protein 2.4 g/L. Gram stain of the cerebrospinal fluid shows gram-positive cocci in chains. Which antibiotic provides the necessary coverage against this organism?
- A.AmpicillinCorrect
- B.Doxycycline
- C.Ceftriaxone
- D.Vancomycin
Explanation
Gram-positive cocci in chains in neonatal cerebrospinal fluid indicate group B streptococcus, the leading cause of neonatal meningitis, and ampicillin is the agent that reliably covers it. Ampicillin is also the only one of these choices that covers Listeria monocytogenes, an intrinsically cephalosporin-resistant gram-positive rod that is the other classic neonatal pathogen, which is why ampicillin remains a fixed component of every empiric neonatal regimen. Standard empiric therapy for suspected neonatal meningitis is ampicillin plus cefotaxime, with gentamicin frequently added for synergy and gram-negative coverage until cultures return; the cephalosporin and aminoglycoside address Escherichia coli and other gram-negative organisms. Ceftriaxone is deliberately avoided in the neonatal period because it displaces bilirubin from albumin and increases the risk of kernicterus, and because it precipitates with calcium-containing intravenous solutions, causing potentially fatal intravascular precipitates; cefotaxime is used instead. Vancomycin is reserved for suspected methicillin-resistant staphylococcal or coagulase-negative staphylococcal infection, typically catheter-related late-onset sepsis, and is not the drug of choice for group B streptococcus, which remains uniformly penicillin susceptible. Doxycycline and other tetracyclines are contraindicated in neonates and children under 8 years for most indications because of dental staining. Group B streptococcal meningitis is treated with high-dose penicillin or ampicillin for at least 14 days, with repeat lumbar puncture to confirm sterilization.
Why each option
- A.
- Correct. Ampicillin covers group B streptococcus and Listeria monocytogenes and is a fixed part of empiric neonatal therapy.
- B.
- Doxycycline is contraindicated in neonates and does not treat central nervous system streptococcal infection.
- C.
- Ceftriaxone is avoided in neonates because it displaces bilirubin and precipitates with calcium; cefotaxime is substituted.
- D.
- Vancomycin is reserved for resistant staphylococcal infection and is not first choice for penicillin-susceptible group B streptococcus.
Reference: AAP Red Book, 2024, Group B Streptococcal Infections
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