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Acute Bacterial Meningitis

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In cases of suspected meningococcal meningitis/septicaemia, antibiotics should be administered immediately, ideally before hospital referral. If already in the hospital, give antibiotics before performing a lumbar puncture.

Initial Bacterial Meningitis Management Summary
ABC stabilization, admit for lumbar puncture (LP). Perform CT if signs suggest space-occupying lesion (SOL). Take blood cultures and, if feasible, cerebrospinal fluid (CSF) cultures. Empirical antibiotic therapy: IV Cefotaxime 2g every 4 hours or Ceftriaxone 2g IV twice daily. Add IV Amoxicillin 2g every 4 hours if Listeria is suspected, especially in patients over 50 years, pregnant, or immunocompromised. Add IV Vancomycin (15-20 mg/kg) if Pseudomonas infection is suspected or if high rates of resistant organisms are prevalent. Add IV Aciclovir 10 mg/kg TDS if HSV encephalitis is under consideration. Administer Dexamethasone 0.15 mg/kg (usually 10 mg IV initially) every 6 hours for 4 days, ideally started before or at the time of the first antibiotic dose.

Initial Bacterial Meningitis Management Summary

ABC stabilization, admit for lumbar puncture (LP). Perform CT if signs suggest space-occupying lesion (SOL).
Take blood cultures and, if feasible, cerebrospinal fluid (CSF) cultures.
Empirical antibiotic therapy: IV Cefotaxime 2g every 4 hours or Ceftriaxone 2g IV twice daily.
Add IV Amoxicillin 2g every 4 hours if Listeria is suspected, especially in patients over 50 years, pregnant, or immunocompromised.
Add IV Vancomycin (15-20 mg/kg) if Pseudomonas infection is suspected or if high rates of resistant organisms are prevalent.
Add IV Aciclovir 10 mg/kg TDS if HSV encephalitis is under consideration.
Administer Dexamethasone 0.15 mg/kg (usually 10 mg IV initially) every 6 hours for 4 days, ideally started before or at the time of the first antibiotic dose.

About

Untreated acute bacterial meningitis has a mortality rate of 70-100%.
Treat based on clinical suspicion alone, initiating Cefotaxime or Ceftriaxone promptly.
Do not delay treatment for test results; always consider Listeria in older or pregnant patients.
Delayed treatment increases mortality and morbidity significantly.
Atypical presentations pose diagnostic challenges.

Aetiology

Caused by bacterial infection in the subarachnoid space.
Common organisms include Pneumococcus, Meningococcus, and Haemophilus influenzae (all are encapsulated, providing resistance against neutrophil phagocytosis).
Bacteria colonize the nasopharynx, producing IgA protease, which damages mucous membranes, facilitating bacterial adherence and invasion.

Pathology

Leads to purulent exudate in the subarachnoid space.
Disrupts cerebral autoregulation and causes localized thrombophlebitis and vasogenic oedema.
Can result in arterial and venous thrombosis, infarction, and protein accumulation, disrupting CSF flow.

Common Organisms Causing Bacterial Meningitis

Organism	Details	Antibiotic
Streptococcus pneumoniae	Primary cause in adults, associated with pneumonia, sinusitis, and otitis media. Higher incidence in alcoholics, diabetics, post-splenectomy, complement deficiency, basal skull fractures, and CSF rhinorrhoea.	Penicillin G if sensitive; Ceftriaxone (2g IV BD) or Cefotaxime (2g IV QID) initially, with Vancomycin (15-20 mg/kg) added if resistance is suspected. 2-week course.
Neisseria meningitidis	Main cause in children and adolescents; petechial rash is common. Risk increased with complement deficiencies.	Penicillin G if sensitive; Ceftriaxone (2g IV BD) or Cefotaxime (2g IV QID).
Haemophilus influenzae	Reduced incidence due to vaccination.	Cefotaxime (2g IV QID) or Ceftriaxone (2g IV BD).
Gram-negative bacteria	Common in diabetics, cirrhotics, or post-craniotomy patients.	Cefotaxime (2g IV QID) or Ceftriaxone (2g IV BD) for 3 weeks.
Group B streptococci	Traditionally a neonatal infection, now seen across all ages.	Penicillin G (3 million units IV every 4 hours) or Ampicillin (2g IV every 4 hours).
Listeria monocytogenes	Common in neonates, pregnant women, immunocompromised, and older adults; often foodborne.	Ampicillin (2g IV every 4 hours) for 3 weeks, sometimes with Gentamicin (5 mg/kg IV daily, divided over 3 doses).
Staphylococcus aureus	Typically follows neurosurgical intervention or certain underlying conditions.	Vancomycin (15-20 mg/kg IV every 12 hours) is preferred.
Cryptococcus neoformans	Common in immunocompromised individuals.	Amphotericin B (0.7 mg/kg IV daily) plus flucytosine (100 mg/kg divided into four doses) for 2 weeks, followed by fluconazole (400 mg daily) for maintenance.

Clinical Presentation

Symptoms: Headache, fever, altered consciousness, neck stiffness, rash, seizures, or shock.
Additional history: Recent chest infection, craniotomy, or rhinorrhoea.
Petechial rash (non-blanching), neck stiffness, and Kernig’s or Brudzinski’s sign may be present.
Signs often muted in young, elderly, or immunocompromised patients.
Late-stage symptoms: VI nerve palsy, papilledema, decreased consciousness, and other signs of intracranial pressure.

Complications

Seizures, stroke, hyponatremia, increased intracranial pressure (ICP), hydrocephalus, cerebral abscess, and herniation.

Investigations

Blood tests: FBC, U&E, LFTs, CRP, glucose.
CT scan if ICP is suspected (papilledema, altered consciousness).
CSF analysis: Glucose, protein, lactate, microscopy, culture, PCR for specific pathogens.
Biopsy of petechial lesions if necessary.

CSF Analysis for Common Meningitis Types

Parameter	Normal	Bacterial	Viral	Tuberculous	Fungal
Appearance	Clear	Turbid	Clear	Cloudy	Cloudy
Opening Pressure	12-20 cm CSF	Raised	Normal to mildly raised	Raised	Raised
CSF WBC	<5 cells/µL	High (mainly neutrophils)	High (mainly lymphocytes)	High (mainly lymphocytes)	High (mainly lymphocytes)
CSF Protein	Normal	Raised	Mildly raised	Markedly raised	Raised
CSF Plasma Glucose Ratio	>0.66	Low	Normal to slightly low	Very low	Low

Management

Immediate treatment: Stabilize with ABCs, fluid resuscitation, and early antibiotics.
Antibiotic therapy:
- Pre-hospital: IV or IM Benzylpenicillin or Cefotaxime based on age and severity.
- In hospital: IV Ceftriaxone or Cefotaxime, add Amoxicillin if Listeria is suspected, and Vancomycin if Pseudomonas risk is high.
Adjunct therapy: Dexamethasone 0.15 mg/kg every 6 hours for 4 days.
Prophylaxis: For contacts, Rifampicin 600 mg twice daily for 2 days, or alternative as per guidelines.

When to Seek Critical Care Support

Seek critical care support for patients with rapidly progressing rash, low GCS, severe hypotension, or poor response to initial treatment.

References

Acute Bacterial Meningitis - Norfolk and Norwich Guidelines

PLEASE NOTE LEGAL ADVICE: The contents are under continuing development and improvements and may contain errors of omission or fact. Feedback vital and always welcome at drokane at gmail.com. This is not to be used for the assessment, diagnosis or management of patients. It should not be regarded as medical advice. It is only for educational purposes. Please adhere to your local protocols. If you are unwell please seek healthcare advice from your doctor. This does not replace senior or specialist advice. If you do not accept this then please do not use the website. If you need medical advice, please consult a doctor or other appropriate medical professional. If you are a medical professional and you need advice then speak to your senior or colleagues.

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