A 45-year-old immunocompetent adult with no prior antibiotic therapy presents with acute bacterial meningitis (fever, neck stiffness, photophobia). CSF shows glucose 18 mg/dL (serum 90 mg/dL), protein 420 mg/dL, TLC 3200 cells/µL with 92% neutrophils. Gram stain is negative. Which empirical antibiotic combination is most appropriate pending culture results?
- A Vancomycin alone pending culture and sensitivity results
- B Metronidazole plus ceftriaxone (anaerobic coverage is essential)
- C Ceftriaxone 2g IV every 12 hours PLUS dexamethasone 0.15 mg/kg every 6 hours (first dose before antibiotics) ✓
- D Ampicillin alone (adequate for community-acquired Streptococcal meningitis)
Explanation
For community-acquired bacterial meningitis in adults (age 18–50), the empirical regimen is ceftriaxone (covers S. pneumoniae and N. meningitidis) plus dexamethasone 0.15 mg/kg every 6 hours × 4 days to reduce neurological complications. Dexamethasone must be given with or just before the first antibiotic dose to suppress the inflammatory response triggered by bacterial lysis. Vancomycin is added in areas with high penicillin-resistant S. pneumoniae prevalence. Metronidazole is added if brain abscess or post-neurosurgical meningitis is suspected. Ampicillin monotherapy is inadequate.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.