Bacterial meningitis: lumbar puncture findings, empirical antibiotics and management
RezzyBacterial meningitis is an absolute classic for the UKMLA AKT—it's high-stakes, high-yield, and requires you to know exactly what to do when the clock is ticking.
To get us started, I'll find a visual guide to help you visualize the clinical presentation and the diagnostic pathway.
That image gives a solid overview of the clinical picture, but for the AKT, you really need to be able to distinguish between the different types of meningitis based on the Cerebrospinal Fluid (CSF) results.
I've put together a comparison table for you to help you spot the "bacterial" pattern instantly.
| Feature | Normal | Bacterial | Viral | Tuberculous (TB) |
|---|---|---|---|---|
| Appearance | Clear/Straw | Cloudy/Turbid | Clear | Fibrin web |
| Opening Pressure | 10-20 cmH2O | High (>25) | Normal/High | High |
| WBC Count | <5 cells/mm³ | High (>1000) | 10-1000 | 10-500 |
| Predominant Cell | Lymphocytes | Neutrophils | Lymphocytes | Lymphocytes |
| Glucose | >60% of blood | Low (<40%) | Normal | Very Low (<30%) |
| Protein | 0.15-0.45 g/L | High (>1.0) | Normal/High | Very High (>1.0) |
In the UK, management follows strict NICE guidelines. Here is the breakdown of how you handle a suspected case:
1. Pre-Hospital Management
If you're a GP and you see a patient with a non-blanching rash and suspected meningitis, give IM Benzylpenicillin immediately (unless they have a severe penicillin allergy) and call 999. Don't wait—time is brain!
2. Empirical Antibiotics (Hospital)
Once in the hospital, the choice of antibiotic depends on the patient's age and risk factors:
- Standard (Adults <55 years): IV Ceftriaxone (2g BD) or Cefotaxime.
- Older Adults (>55 years) or Immunocompromised: Add IV Amoxicillin (or Ampicillin) to cover for Listeria monocytogenes.
3. Adjunctive Therapy
- Dexamethasone: This is high-yield! Give
0.15 mg/kgQDS. It should be given with or just before the first dose of antibiotics. If the antibiotics have already been running for more than 12 hours, don't bother starting it. It helps reduce neurological complications like hearing loss.
4. Public Health & Prophylaxis
- Notify: Meningitis is a notifiable disease. You must inform the local Public Health team.
- Contacts: Close "household-type" contacts of patients with Meningococcal meningitis need prophylaxis, usually with a single dose of Ciprofloxacin.
Mnemonic: "C" for Meningitis Ceftriaxone (Treatment), Ciprofloxacin (Contacts), Cloudy CSF, Complement deficiency (Risk factor).
Since these CSF values and antibiotic choices are so specific, would you like to try a quick game to see if you can group the findings correctly?
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