Overview
Bacterial Meningitis in Adults
Topic Overview
Summary
Bacterial meningitis is inflammation of the meninges caused by bacterial infection. It is a medical emergency with high mortality (15-25%) without treatment. The classic triad is fever, neck stiffness, and altered mental status, though all three are present in fewer than 50% of cases. Empirical antibiotics (ceftriaxone + dexamethasone) must be given within 1 hour of presentation. LP confirms diagnosis but should NOT delay antibiotics.
Key Facts
- Organisms: Streptococcus pneumoniae (most common in adults), Neisseria meningitidis
- Classic triad: Fever + neck stiffness + altered mental status (complete triad in under 50%)
- Treatment: Ceftriaxone 2g IV + dexamethasone 0.15mg/kg IV — within 1 HOUR
- LP: Do NOT delay antibiotics if LP cannot be performed promptly
- Rash: Non-blanching petechial/purpuric rash = assume meningococcal disease
- Contacts: Require chemoprophylaxis (ciprofloxacin or rifampicin)
Clinical Pearls
If meningitis is suspected: GIVE ANTIBIOTICS FIRST, LP second
Dexamethasone reduces mortality in pneumococcal meningitis — give BEFORE or WITH first dose of antibiotics
Non-blanching rash = meningococcal disease — notify PHE immediately
Why This Matters Clinically
Meningitis is a time-critical emergency. Every hour delay in antibiotics increases mortality by 10-15%. All clinicians must recognise the clinical features and know to give empirical treatment immediately. Contact tracing and public health notification are legally required.
Visual Summary
Visual assets to be added:
- Meningococcal rash photograph
- LP positioning and technique
- CSF analysis comparison table
- Treatment algorithm flowchart
Epidemiology
Incidence
- UK: ~2000 cases/year of bacterial meningitis
- Incidence: 1-2 per 100,000/year in adults
- Mortality: 15-25% (higher in pneumococcal, older adults)
- Morbidity: 15-20% of survivors have long-term sequelae
Organisms by Age
| Age Group | Common Organisms |
|---|---|
| Adults (16-60) | S. pneumoniae (50%), N. meningitidis (25%), Listeria (5%) |
| Over 60 / Immunocompromised | S. pneumoniae, Listeria monocytogenes, Gram-negatives |
Risk Factors
| Factor | Associated Organisms |
|---|---|
| Splenectomy / asplenia | S. pneumoniae, N. meningitidis |
| CSF leak / skull fracture | S. pneumoniae |
| Cochlear implant | S. pneumoniae |
| Over 50 / Immunocompromised | Listeria monocytogenes |
| Recent neurosurgery / VP shunt | Staph epidermidis, S. aureus, Gram-negatives |
| Close contacts | N. meningitidis |
Pathophysiology
Route of Infection
- Haematogenous spread: Most common (nasopharyngeal carriage → bacteraemia → meningeal seeding)
- Direct spread: From sinusitis, otitis media, mastoiditis
- Direct inoculation: Post-neurosurgery, trauma
Inflammatory Cascade
- Bacteria enter subarachnoid space
- Local multiplication → release of PAMPs
- Activation of TLRs → cytokine release (IL-1β, TNF-α, IL-6)
- BBB disruption → vasogenic oedema
- Neutrophil influx → cytotoxic oedema
- Increased ICP → decreased cerebral perfusion
- Neuronal injury → death/sequelae
Why Dexamethasone Helps
- Reduces inflammatory response
- Attenuates cytokine-mediated damage
- Reduces hearing loss and mortality (especially in pneumococcal)
Clinical Presentation
Classic Triad (All Three in Under 50%)
Other Features
Red Flags
| Feature | Significance |
|---|---|
| Non-blanching rash | Meningococcal disease — treat immediately |
| GCS under 12 | Severe — consider ICU |
| New focal signs | CT before LP; intracranial complication |
| Rapidly progressive illness | High mortality |
| Shock | Meningococcal septicaemia |
Fever (85-95%)
Common presentation.
Neck stiffness (85%)
Common presentation.
Altered mental status/decreased GCS (70%)
Common presentation.
Clinical Examination
Vital Signs
- Fever (may be absent in immunocompromised or elderly)
- Tachycardia
- Hypotension (septic shock)
Neurological Examination
Signs of Meningism:
- Neck stiffness: Resistance to passive flexion
- Kernig's sign: Knee extension with hip flexed causes pain
- Brudzinski's sign: Neck flexion causes hip/knee flexion
GCS Assessment: Document carefully — prognostic
Focal Signs: Cranial nerve palsies, hemiparesis (suggests complication)
Skin Examination
- Petechiae / purpura — especially in pressure areas
- "Glass test" — non-blanching = do NOT delay treatment
Fundoscopy
- Papilloedema suggests raised ICP (CT before LP)
Investigations
Do NOT Delay Antibiotics for Investigations
Lumbar Puncture (If Safe)
Defer LP if:
- Signs of raised ICP (papilloedema, GCS under 12, focal signs)
- Coagulopathy (INR over 1.3, platelets under 50)
- Infection at LP site
- Haemodynamic instability
CSF Findings:
| Parameter | Bacterial | Viral |
|---|---|---|
| Appearance | Turbid/cloudy | Clear |
| WCC | Over 1000 (neutrophils) | Under 1000 (lymphocytes) |
| Protein | Raised (over 1 g/L) | Normal/mildly raised |
| Glucose | Low (under 50% serum) | Normal |
Blood Tests
- Blood cultures (before antibiotics if under 30 min delay)
- FBC, U&E, LFTs, CRP
- Coagulation (if LP planned)
- Serum glucose (for CSF:serum ratio)
- Lactate (prognostic)
- Procalcitonin (if available)
Imaging
- CT Head: Before LP if indication for deferral
- Do NOT delay LP for CT unless specific indication
Microbiology
- CSF Gram stain + culture + PCR
- Blood cultures
- Throat swab (meningococcal carriage)
Classification & Staging
By Organism
| Organism | Features |
|---|---|
| S. pneumoniae | Most common; high mortality; associated with otitis/sinusitis |
| N. meningitidis | Classic rash; contacts need prophylaxis; notifiable |
| Listeria | Over 50, immunocompromised, pregnancy; requires amoxicillin |
| Gram-negatives | Neurosurgery, elderly, neonates |
| Staph | Post-neurosurgery, VP shunts |
Meningococcal Serogroups
- UK: B, C (C reduced by vaccination), W, Y
- MenB vaccine now in childhood schedule
Management
Immediate Treatment (Within 1 Hour)
1. Dexamethasone:
- 0.15 mg/kg (max 10mg) IV QDS × 4 days
- Give BEFORE or WITH first dose of antibiotics
- Main benefit in pneumococcal meningitis
2. Empirical Antibiotics:
| Patient Group | Regimen |
|---|---|
| Adults (16-60) | Ceftriaxone 2g IV BD |
| Over 60 / Immunocompromised | Ceftriaxone 2g IV BD + Amoxicillin 2g IV 4-hourly (Listeria cover) |
| Penicillin allergy | Chloramphenicol 25mg/kg QDS |
| Post-neurosurgery | Meropenem + Vancomycin |
Duration
- Pneumococcal: 10-14 days
- Meningococcal: 7 days
- Listeria: 21+ days
Supportive Care
- IV fluids (isotonic, avoid overhydration)
- Seizure management if needed
- ICU for GCS under 12, shock, or ARDS
Contact Tracing & Prophylaxis (Meningococcal)
| Contact Type | Prophylaxis |
|---|---|
| Close contacts (household, kissing) | Ciprofloxacin 500mg single dose PO |
| Index case (before discharge) | Ciprofloxacin 500mg PO (clears carriage) |
Public Health Notification
- Meningococcal disease is NOTIFIABLE
- Contact PHE/local HPT immediately
- Duty doctor: 24/7 PHE advice
Complications
Acute
- Raised ICP: Cerebral oedema
- Seizures: 20-40%
- Septic shock: Especially meningococcal
- DIC: Associated with purpuric rash
- SIADH: Hyponatraemia
- Hydrocephalus
- Cerebral venous thrombosis
Long-Term Sequelae (15-20% of survivors)
- Hearing loss (especially pneumococcal — need audiometry)
- Cognitive impairment
- Limb loss (meningococcal septicaemia)
- Focal neurological deficits
- Epilepsy
Prognosis & Outcomes
Mortality
- Overall: 15-25%
- Pneumococcal: 25-30%
- Meningococcal: 10-15%
- Listeria: 20-30%
Prognostic Factors
| Factor | Impact |
|---|---|
| GCS under 10 | Poor prognosis |
| Seizures within 24h | Poor prognosis |
| Delay to antibiotics | 10-15% increase mortality per hour |
| Dexamethasone | Reduces mortality in pneumococcal |
| Age over 60 | Higher mortality |
| Immunocompromise | Higher mortality |
Evidence & Guidelines
Key Guidelines
- NICE CG102: Bacterial Meningitis and Meningococcal Disease
- PHE Meningococcal Disease Guidelines
- ESCMID Guidelines for Bacterial Meningitis
Key Trials
- European Dexamethasone Trial (2002): Dexamethasone reduces mortality and hearing loss in pneumococcal meningitis
Patient & Family Information
What is Bacterial Meningitis?
Meningitis is an infection of the lining of the brain and spinal cord. Bacterial meningitis is less common but more serious than viral meningitis and needs urgent antibiotic treatment.
Warning Signs
- High fever
- Severe headache
- Stiff neck
- Sensitivity to light
- Confusion or drowsiness
- Rash that doesn't fade when pressed (use glass test)
What to Do
- Call 999 immediately if someone has these symptoms
- Bacterial meningitis is a medical emergency
After Treatment
- Most people recover, but some may have long-term problems like hearing loss
- Hearing tests are recommended after recovery
Contacts
- Close contacts may need antibiotics to prevent infection
- Public health will advise on this
Resources
References
Primary Guidelines
- NICE. Meningitis (Bacterial) and Meningococcal Septicaemia in Under 16s: Recognition, Diagnosis and Management (CG102). 2010. nice.org.uk
- PHE. Meningococcal Disease: Guidance and Data. 2023. gov.uk
Key Studies
- De Gans J, van de Beek D. Dexamethasone in adults with bacterial meningitis. N Engl J Med. 2002;347(20):1549-1556. PMID: 12432041
- van de Beek D, et al. Clinical features and prognostic factors in adults with bacterial meningitis. N Engl J Med. 2004;351(18):1849-1859. PMID: 15509818