A 24-year-old male university student is brought to the emergency department with high fever, severe headache, photophobia, and neck stiffness. Lumbar puncture reveals opening pressure of 260 mm H2O, CSF WBC of 2,400 cells/mm^3 with 92% neutrophils, protein of 220 mg/dL, and CSF glucose of 18 mg/dL (serum glucose 95 mg/dL). Which empirical antimicrobial regimen should be initiated immediately along with dexamethasone?

Answer and explanation

Correct answer: C. Intravenous ceftriaxone plus vancomycin

  1. Step 1: Interpret CSF findings: Marked neutrophilic pleocytosis, elevated protein, low CSF-to-serum glucose ratio (< 0.4), and high opening pressure indicate acute bacterial meningitis (most commonly Streptococcus pneumoniae or Neisseria meningitidis).
  2. Step 2: Empirical therapy in immunocompetent young adults is high-dose IV ceftriaxone (2 g q12h) plus vancomycin (to cover penicillin-resistant pneumococci), accompanied by adjunctive IV dexamethasone to reduce neurological sequelae and hearing loss.
Answer
Intravenous ceftriaxone plus vancomycin.
Why not the others: 'Oral amoxicillin' cannot achieve bactericidal CSF concentrations and does not cover resistant strains; 'Acyclovir plus fluconazole' treats viral and fungal meningitis; 'Metronidazole plus gentamycin' covers intra-abdominal anaerobes and enteric rods, not typical meningitis pathogens.

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