Key Facts

Bacterial meningitis is a medical emergency requiring immediate empirical antibiotic treatment. Delayed treatment dramatically increases mortality and morbidity. The causative organism varies by age, and adjunctive dexamethasone improves outcomes in pneumococcal meningitis.

Epidemiology

• UK: ~1,000–2,000 cases/year of bacterial meningitis
• S. pneumoniae: most common in adults; ~30% mortality
• N. meningitidis: most common in children/adolescents; declining with vaccination
• Listeria: elderly, immunocompromised, pregnancy; ~20–30% mortality
• Neonatal GBS meningitis: ~0.3 per 1,000 live births

Aetiology

• Neonates (<3 months): Group B Streptococcus, E. coli, Listeria monocytogenes
• Children (3 months–5 years): N. meningitidis, S. pneumoniae, H. influenzae (rare post-Hib vaccine)
• Adults: S. pneumoniae (most common), N. meningitidis
• Elderly/immunocompromised: S. pneumoniae, Listeria, Gram-negatives
• Post-neurosurgical: S. aureus, coagulase-negative staphylococci, Gram-negatives

Pathophysiology

• Bacteraemia → crossing blood-brain barrier (BBB) → subarachnoid space infection
• Bacterial components (LPS, peptidoglycan) trigger innate immune response in CSF
• Cytokines (TNF-α, IL-1) → meningeal inflammation → BBB disruption → cerebral oedema
• Raised intracranial pressure → reduced cerebral perfusion → neuronal injury
• Vasculitis → cerebral infarction
• Cochlear damage → sensorineural deafness (especially S. pneumoniae)

Adults

• Headache: severe, global
• Fever: high-grade
• Neck stiffness (meningism): pain on flexion
• Altered mental status: confusion, drowsiness → GCS decline
• Photophobia
• Nausea and vomiting
• Seizures: ~20% of cases
• Kernig and Brudzinski signs: sensitivity ~5% (poor sensitivity, high specificity)

Infants/Children

• Non-specific: irritability, poor feeding, lethargy
• High-pitched cry
• Bulging fontanelle (infants)
• Neck stiffness may be absent in young infants
• Seizures
• Non-blanching rash (meningococcal)

Red Flags

• Rapidly declining GCS
• Signs of raised ICP: papilloedema, focal neurology, bradycardia + hypertension + abnormal breathing (Cushing triad)
• Non-blanching purpuric rash
• Seizures
• Shock (septicaemia component)
• Immunocompromised or extremes of age

Bedside

• GCS assessment: serial monitoring
• Blood glucose: paired with CSF glucose
• Blood gas: lactate, acidosis

Bloods (BEFORE LP)

• Blood cultures: essential — positive in 50–70%
• FBC, CRP, lactate: infection markers
• U&Es: SIADH (hyponatraemia)
• Coagulation: DIC screen
• Meningococcal/pneumococcal PCR: on EDTA blood

LP (if no contraindications)

• Contraindications to immediate LP: GCS ≤12, focal neurology, papilloedema, haemodynamic instability, coagulopathy, local skin infection, signs of raised ICP
• CT head before LP: if any of the above
• CSF analysis: appearance, WCC (differential), protein, glucose (+ paired blood glucose), Gram stain, culture, PCR (meningococcal, pneumococcal)
• Opening pressure: typically elevated

Imaging

• CT head: before LP if indicated (see above); excludes space-occupying lesion/hydrocephalus
• MRI: if complications suspected (abscess, cerebral venous sinus thrombosis)

Non-pharmacological

• ABC approach: secure airway if GCS declining
• Do NOT delay antibiotics for any investigation
• Isolation: droplet precautions for meningococcal disease until 24 hours of effective treatment
• Fluid management: avoid overhydration (risk of cerebral oedema); maintain euvolaemia
• ICU referral: GCS ≤12, haemodynamic instability, seizures

Pharmacological

Empirical antibiotics (NICE CG102):

• IV ceftriaxone 2g BD (adult) — start immediately
• Add IV amoxicillin 2g QDS if Listeria suspected (age >60, immunocompromised, pregnant)
• Neonates: cefotaxime + amoxicillin (ampicillin equivalent)
• Post-neurosurgical: vancomycin + meropenem

Adjunctive dexamethasone:

• Dexamethasone 0.15mg/kg (max 10mg) QDS IV for 4 days — give with or before first antibiotic dose
• Evidence: reduces mortality and hearing loss in pneumococcal meningitis (European Dexamethasone study, de Gans et al.)
• Discontinue if non-pneumococcal meningitis confirmed (benefit less clear for meningococcal)

Duration:

• N. meningitidis: 5–7 days
• S. pneumoniae: 10–14 days
• Listeria: 21 days (ampicillin + gentamicin)
• GBS (neonatal): 14–21 days

Close contacts (meningococcal):

• Ciprofloxacin 500mg stat (adult) or rifampicin 600mg BD for 2 days

Referral Criteria

• All cases: infectious diseases, ICU consideration
• Neurosurgery: hydrocephalus, abscess
• Audiology: all bacterial meningitis survivors (hearing assessment)
• Public health: notification (meningococcal); contact tracing

• S. pneumoniae meningitis: mortality 20–30%; neurological sequelae in 30–50% of survivors
• N. meningitidis meningitis: mortality 5–10%
• Listeria meningitis: mortality 20–30%
• Neonatal GBS meningitis: mortality 10%; neurodevelopmental sequelae in 25–50%
• Overall hearing loss: ~10% (higher with S. pneumoniae — up to 30%)
• Cognitive impairment: 10–30% of survivors
• Dexamethasone: reduces mortality from 34% to 14% in pneumococcal meningitis (de Gans trial)
• Delay in antibiotics: each hour increases mortality by 3–10%

CSF Interpretation

Empirical Antibiotics by Age