Bacterial Meningitis

Aetiology

Commonly a complication of ENT/facial infections, cranial trauma or blood-borne infection.

Common organisms that cause meningitis are:

• Meningococcus (B + C) – Niesseria meningitidis (37% of all CABM)
• Pneumococcus – Streptococcus pneumoniae (51%)
• Haemophilus Influenza B (Hib) (rarer now vaccinated)
• Tuberculosis
• Others e.g. listeria (more common in the elderly population); Lyme disease (think travel/tic borne); cryptococcus (more common in HIV/immunocomprimised)

Pathogenesis

1. Attach/invade the pharyngeal mucosa (usually)
2. Get into the blood supply and spread
3. Cross the BBB (mechanism unclear)
4. Toxic products/ immune response causes damage

Signs/symptoms

• Fever; Stiff neck; Altered conscious level (GCS); Headache; Nausea & vomiting; Photophobia; lethargy; confusion
• Meningococcaldisease usually produces a non-blanching purpuric rash
• Papilloedema
• Kernig’s sign- painful knee extension while lying supine

NB signs and symptoms may be atypical in extremes of age or immunocomprimised individuals

Management

Admission to hospital is required if there are signs of meningeal irritation; loss of consciousness; petechial rash; febrile/unwell and fitting; known contact with meningococcal infection.

NB In the community setting- antibiotics should be given empirically, whether or not the patient will require an LP.  Meningitis can be life-threatening.

Once in hospital

• ABCDE if necessary
• Blood cultures and coagulation screen
• Give treatment as appropriate (see below)
• Disrupt and swab/aspirate any petechial or purpuric skin lesions for microscopy and culture.
• CTb and MRIb should be done in all patients with papilloedema or focal neurological signs (or other indication of raised ICP)
• Lumbar puncture

Warning signs

• Marked depressed conscious level (GCS<12) or fluctuating conscious level (ΔGCS >2)
• Focal neurological signs
• Seizure before presentation
• Shock (bradycardia/hypotension)
• Papilloedema

Treatment

• General measures
  • Elevate head >30° off bed (increases venous return and decreases ICP)
• Monitor neurological status closely; assess for pain/restlessness regularly
• Administer analgesia as required (AVOID narcotics)
• Manage in a dark, quiet room
• Assess response to treatment regularly

• Antibiotics
  • Empiric (adult)
    • IV Ceftriaxone2g BD
      • + IV Ampicillin/Amoxicillin 2g QDS if listeria is suspected (and in >55yo)
      • IV amphotericin B/ flucytosine / fluconazole if cryptococcus suspected (HIV)
      • Rifampicin, Isoniazid, Pyridostigmine and Ethambutol for TB
    • If Penicillin Allergic
      • Chloramphenicol IV 25mg/kg and Vancomycin IV 500mg QDS
      • + Co-trimoxazole if suspect listeria
  • Empiric treatment (child)
    • Ceftriaxone + amoxicillin (basically as long as there is a 3rd gen cephalosporin: ceftriaxone/cefotaxime (2nd gen: cefuroxime can be used too- more useful for resistant infections) to cover Niesseria/E coli and a penicillin to cover strep, I think you’re covered.  Gentamicin will help the action of penicillins and will provide some coverage against gram negatives BUT it has ototoxic/nephrotoxic risk so a risk/benefit decision should be made there and then.  In general, I don’t think it is first line, but as soon as cultures come back, should be added if appropriate)
      • If group B strep: benzylpenicillin and gentamicin
      • If listeria: amoxicillin and gentamicin
    • If paracetamol hypersensitive: as adult
• Steroids
  • Give to all patients suspected of bacterial meningitis:
    • 10mg IV 15-20mins BEFORE or with the first dose of antibiotic, then every 6 hours
  • Improves survival
  • Contraindicated in post-surgical meningitis; severely immunocomprimised; meningococcal/septic shock or hypersensitivity

Prognosis

• Worse if showing organ failure/distress or increasing sepsis