Approach to Bacterial Meningitis
Immediate Actions (Within 1 Hour of Presentation)
Administer empiric antibiotics within 60 minutes of hospital arrival—delays beyond this window significantly increase mortality and neurological sequelae. 1, 2
Time-Critical Sequence
- Obtain blood cultures immediately but do not delay antibiotics beyond 1 hour to acquire them 1, 2
- Assess for CT scan indications (age ≥60, immunocompromise, prior CNS disease, new seizure, papilledema, altered consciousness [GCS <10], focal neurological deficits) 1
- If NO CT indications present: Proceed directly to lumbar puncture after blood cultures 1
- If CT IS indicated: Give antibiotics first, then obtain CT, then perform LP only if no mass effect 1
- Start dexamethasone with or 10–20 minutes before the first antibiotic dose 1, 3
Empiric Antibiotic Regimens by Age and Risk Factors
Neonates (≤4 weeks)
| Age | Regimen |
|---|---|
| <1 week | Ampicillin 50 mg/kg IV q8h + Cefotaxime 50 mg/kg IV q8h ± Gentamicin 2.5 mg/kg IV q12h [1,2] |
| 1–4 weeks | Ampicillin 50 mg/kg IV q6h + Cefotaxime 50 mg/kg IV q6–8h ± Gentamicin 2.5 mg/kg IV q8h [1,2] |
- Never use ceftriaxone in neonates due to risk of fatal calcium-ceftriaxone precipitation 3
Children (1 month–18 years)
Ceftriaxone 50 mg/kg IV q12h (max 2 g/dose) OR Cefotaxime 75 mg/kg IV q6–8h PLUS Vancomycin 10–15 mg/kg IV q6h (target trough 15–20 µg/mL) 1, 2
- Alternative: Rifampicin 10 mg/kg IV q12h (max 600 mg/day) may replace vancomycin in low-resistance areas 1, 2
Adults 18–50 Years (Immunocompetent)
Ceftriaxone 2 g IV q12h (or 4 g IV q24h after first 24 hours) OR Cefotaxime 2 g IV q4–6h PLUS Vancomycin 10–20 mg/kg IV q8–12h (target trough 15–20 µg/mL) 1, 2
Adults ≥50 Years OR Immunocompromised (Any Age)
Ceftriaxone 2 g IV q12h OR Cefotaxime 2 g IV q4–6h PLUS Vancomycin 10–20 mg/kg IV q8–12h PLUS Ampicillin 2 g IV q4h (or Amoxicillin 2 g IV q4h) 1, 2
- The ampicillin is mandatory to cover Listeria monocytogenes, which cephalosporins cannot treat 1, 2
- Listeria risk factors: age >50, diabetes, immunosuppressive therapy, malignancy, other immunocompromising conditions 1, 2
Adjunctive Dexamethasone Therapy
Dosing
- Adults: 10 mg IV q6h for 4 days 4, 1
- Children: 0.15 mg/kg IV q6h for 2–4 days 1, 3
- Neonates: Do NOT use dexamethasone—insufficient evidence and potential harm 1
Timing and Duration
- Give with or 10–20 minutes before the first antibiotic dose 1, 3
- If omitted initially, may still start up to 4 hours (some sources say 12 hours) after antibiotics 4, 1
- Continue for 4 days if pneumococcal meningitis confirmed or probable 4, 1
- Stop if alternative etiology identified (viral, tuberculous) 4, 1
- Greatest benefit: Pneumococcal and H. influenzae meningitis—reduces mortality (7% vs 15%) and unfavorable outcomes (15% vs 25%) 1
Special Considerations
- Do NOT give dexamethasone to children with meningococcal septicemia (purpuric rash with shock) unless inotrope-resistant shock develops 3
- Dexamethasone may reduce vancomycin CSF penetration; consider adding rifampicin 300 mg IV q12h to the regimen when dexamethasone is used 1
Lumbar Puncture Decision Algorithm
Contraindications to Immediate LP
- Rapidly evolving purpuric rash with cardiovascular instability 3
- Glasgow Coma Scale ≤12 4, 1
- Focal neurological deficits (gaze palsy, facial weakness, limb drift) 1
- New seizure within past week 1
- Papilledema or signs of raised intracranial pressure 1
- Immunocompromised state 1
- Prior CNS disease (mass lesion, stroke, focal infection) 1
- Coagulopathy or thrombocytopenia 3
- Need for intubation 3
If any contraindication present: Give antibiotics immediately, defer LP until stable 1, 3
Isolated brief seizures in children should NOT delay LP—seizures occur in 30% of pediatric bacterial meningitis cases 1
Expected CSF Findings in Bacterial Meningitis
| Parameter | Typical Finding | Clinical Significance |
|---|---|---|
| Opening pressure | 200–500 mm H₂O | Raised intracranial pressure [1] |
| WBC count | 1,000–5,000 cells/µL (range 100–110,000) | Intense inflammation [1] |
| Differential | Neutrophils 80–95% (≈10% may be lymphocyte-predominant) | Supports bacterial etiology [1] |
| Glucose | <40 mg/dL in 50–60% of cases | Bacterial consumption [1] |
| CSF/serum glucose ratio | <0.4 in children >12 months; <0.6 in neonates | Distinguishes bacterial from viral [1] |
| Protein | Elevated | Blood-brain barrier disruption [1] |
Gram Stain Sensitivity
- Overall: 60–90% sensitive, 97% specific 1
- S. pneumoniae: 90% positive 1
- H. influenzae: 86% positive 1
- N. meningitidis: 75% positive 1
- Gram-negative bacilli: 50% positive 1
- Listeria: 33% positive 1
Pathogen-Specific Definitive Therapy (After Culture Results)
| Pathogen | Susceptibility | Recommended Therapy | Duration |
|---|---|---|---|
| S. pneumoniae | Penicillin-sensitive (MIC <0.1) | Penicillin G or Ampicillin [2] | 10–14 days [2] |
| Penicillin-intermediate (MIC 0.1–1.0) | Ceftriaxone or Cefotaxime [2] | 10–14 days [2] | |
| Penicillin/cephalosporin-resistant (MIC ≥2) | Vancomycin + Ceftriaxone [2] | 10–14 days [2] | |
| N. meningitidis | Any | Ceftriaxone or Penicillin G [2] | 5–7 days [2] |
| Listeria | — | Ampicillin 2 g IV q4h [2] | 21 days [2] |
| H. influenzae | — | Ceftriaxone or Cefotaxime [2] | 10 days [2] |
Fluid Resuscitation and Shock Management (Pediatrics)
- Give 20 mL/kg isotonic crystalloid boluses rapidly, reassessing after each dose 3
- Up to 60 mL/kg may be required in first hour for severe meningococcal sepsis 3
- If >40 mL/kg needed or shock persists: Consult pediatric intensive care immediately for inotropic support 3
- Early ventilatory support should be considered once inotropes are started 1
ICU Transfer Criteria
Transfer to intensive care immediately if any of the following:
- Rapidly evolving purpuric rash 4, 3
- GCS ≤12 (or drop of >2 points) 4
- Cardiovascular instability or hypoxia 4
- Requiring >40 mL/kg fluid resuscitation 3
- Uncontrolled or frequent seizures 4
- Respiratory compromise 3
- Evidence of severe sepsis 4
Regional Resistance Considerations
- In areas with high pneumococcal penicillin/cephalosporin resistance: Add vancomycin or rifampicin to ceftriaxone/cefotaxime 1, 2
- After recent travel to high-resistance regions: Add vancomycin empirically 1, 2
- Animal studies show ceftriaxone + vancomycin or rifampicin achieves superior CSF sterilization versus ceftriaxone alone in resistant pneumococcal meningitis 1
Common Pitfalls to Avoid
- Never delay antibiotics for imaging—give antibiotics first, then obtain CT if indicated 1, 2
- Never omit ampicillin in patients ≥50 years or immunocompromised—cephalosporins lack Listeria activity 1, 2
- Never underdose antibiotics—meningitis requires high doses for adequate CSF penetration 1, 2
- Never fail to obtain blood cultures before antibiotics, but do not let this delay treatment beyond 1 hour 1, 2
- Never use vancomycin alone—must be combined with a third-generation cephalosporin 1
- Never give dexamethasone >12 hours after first antibiotic dose—timing is critical for benefit 4, 1
- Never use ceftazidime as empiric therapy for community-acquired meningitis—reserve for Pseudomonas coverage 1
Follow-Up and Chemoprophylaxis
Hearing Assessment
- Perform audiologic evaluation within 4 weeks of discharge—sensorineural hearing loss occurs in 10–30% of survivors 3