Definition
- Acute bacterial (pyogenic) meningitis is inflammation of the meninges caused by pyogenic bacteria.
- It is a medical emergency with high mortality and a risk of serious neurological sequelae if treatment is delayed.
Etiology (age-dependent)
- Neonates — Group B Streptococcus, E. Coli, Klebsiella, Listeria monocytogenes.
- Beyond 3 months — Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae type b (Hib now rare where vaccinated).
- Predisposing factors — otitis media/sinusitis, head trauma/CSF leak, immunodeficiency, and neural-tube defects.
Clinical Features
- Older children — fever, headache, vomiting, photophobia, neck stiffness, altered sensorium and seizures.
- Neonates/infants — non-specific: fever or hypothermia, poor feeding, lethargy, irritability, a high-pitched cry, bulging anterior fontanelle and seizures.
- Signs of meningeal irritation — Kernig's and Brudzinski's signs and neck rigidity (often absent in young infants).
- A petechial/purpuric rash suggests meningococcal disease.
Investigations
- Lumbar puncture & CSF examination — the key investigation.
- Blood culture, CBC, CRP, blood glucose (for CSF:blood glucose ratio), electrolytes.
- CT head before LP if there are signs of raised intracranial pressure, focal deficits or coma (to avoid herniation).
Typical CSF Findings
| Parameter | Pyogenic meningitis |
|---|
| Appearance | Turbid / cloudy |
| Cells | ↑↑ (neutrophils/polymorphs) |
| Protein | Raised |
| Glucose | Low (< ½ blood glucose) |
| Gram stain/culture | Organism seen/grown |
Management
- Prompt empirical IV antibiotics — do not delay for investigations: ceftriaxone/cefotaxime (± vancomycin); add ampicillin for Listeria in neonates.
- Dexamethasone (with or just before the first antibiotic dose) reduces hearing loss, particularly in Hib meningitis.
- Supportive care — airway/oxygen, careful fluids (watch for SIADH), control seizures and raised intracranial pressure, and treat shock.
- Isolation and chemoprophylaxis of close contacts for meningococcal (and Hib) disease.
Complications
- Acute — seizures, raised ICP, SIADH, subdural effusion/empyema, cerebral infarction, shock (meningococcaemia).
- Long-term — sensorineural hearing loss, hydrocephalus, epilepsy, cerebral palsy, and intellectual disability.
Prevention
- Vaccination — Hib, pneumococcal (PCV) and meningococcal vaccines.
- Chemoprophylaxis of close contacts (rifampicin/ciprofloxacin/ceftriaxone) for meningococcal and Hib.
- Early recognition and prompt treatment reduce mortality and sequelae.
Pathophysiology
Bacteria reach the meninges (haematogenous / direct spread) → Inflammation of the meninges & subarachnoid space → Cerebral oedema, raised ICP, impaired CSF flow, vasculitis → Neuronal injury → deficits, seizures, sequelae
CSF in Different Meningitides
| Parameter | Pyogenic | Viral | Tubercular |
|---|
| Cells | ↑↑ Neutrophils | ↑ Lymphocytes | ↑ Lymphocytes |
| Protein | High | Mildly high | Very high |
| Glucose | Low | Normal | Low |
| Appearance | Turbid | Clear | Cobweb clot |
Monitoring & Management of Complications
- Watch for and treat SIADH (fluid restriction), raised ICP, and seizures.
- A persistent fever or focal signs → suspect subdural effusion/empyema (imaging).
- Arrange a hearing assessment on recovery — deafness is the commonest sequela.
Empirical Antibiotic BY Age
| Age | Empirical regimen |
|---|
| Neonate | Ampicillin + cefotaxime (± gentamicin) |
| > 3 months | Ceftriaxone/cefotaxime (± vancomycin) |
Prognosis
- Outcome depends on the organism, the child's age, and — crucially — the speed of starting antibiotics.
- Delay increases mortality and the risk of permanent sequelae such as deafness, hydrocephalus and neurodevelopmental impairment; hence the emphasis on immediate treatment.
Key Supportive Measures
- Maintain airway, oxygenation and circulation; treat shock (especially meningococcaemia).
- Careful fluid management (neither over- nor under-hydrate; watch for SIADH).
- Control seizures and raised intracranial pressure; monitor neurological status closely.