Gram Negative Diplococci
aka Microbial Mystery 001
Consider a 21 year-old presenting to the emergency department with fevers and agitation. His lumbar puncture results are shown below:
| CSF parameter | Result |
|---|---|
| Macroscopic appearance | Cloudy |
| RBC | 8,816 × 10⁶/L |
| WBC | 250 × 10⁶/L |
| Polymorphs | 97% |
| Mononuclear cells | 3% |
| Gram stain | Occasional Gram-negative diplococci |
Questions
Q1. What is the diagnosis?
Meningococcal meningitis
Q2. What is the ‘normal’ ratio of red cells to white cells in the CSF?
500:1
(although this may vary depending on the number of red cells and white cells in the peripheral blood)
Q3. What is the role of steroids in this condition?
Corticosteroid use in Western countries is supported by evidence from a randomised controlled trial performed in Europe:
- de Gans J et al. Dexamethasone in adults with bacterial meningitis. N Engl J Med. 2002 Nov 14;347(20):1549-56.
The points to note about this trial are:
- dexamethasone 10mg QID for 4 days led to a decrease in death and disability in adults treated for bacterial meningitis
- dexamethasone was administered 10-15 minutes before or at the time of antibiotics (no-one knows if there is benefit in administering steroids in any way other than this and there may be harm)
- the benefit was only demonstrated in patients with pneumococcal meningitis in a setting where resistant pneumococcus was rare (no benefit has been demonstrated in meningococcal meningitis)
Two studies from third world countries have failed to demonstrate a benefit:
Greenwood BM. Corticosteroids for acute bacterial meningitis. N Engl J Med. 2007 Dec 13;357(24):2507-9.
CLINICAL CASES
Microbial Mystery
Intensivist in Wellington, New Zealand. Started out in ED, but now feels physically ill whenever he steps foot on the front line. Clinical researcher, kite-surfer | @DogICUma |