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PE27.1 | Acute Bacterial Meningitis — SDL Guide (Part 3)
Self-Assessment
You have now completed the core content of this module on acute bacterial meningitis. The scenarios below are designed to test whether you can apply this knowledge in the integrated, reasoning-forward way that clinical practice demands — not recall isolated facts, but connect the age of the patient to the organism, the organism to the CSF picture, and the CSF picture to the correct empirical treatment. Work through each question before reading the answer. If you find yourself uncertain about the reasoning, return to the relevant section of this module. The ability to hold the age-stratified organism spectrum and the CSF interpretation framework simultaneously in your mind is the core clinical skill this module targets.
Scenario 1: A 7-month-old fully vaccinated child presents with fever for 3 days, one generalised seizure, and lethargy. On examination: febrile 39°C, GCS 13/15, no fontanelle (fontanelle closed), Kernig's sign positive. LP CSF: turbid, WBC 2,200/mm³ (85% PMN), protein 210 mg/dL, glucose 18 mg/dL, serum glucose 90 mg/dL.
Q1: The CSF:serum glucose ratio is approximately ___. (Calculate it.)
Q2: Which single drug class provides coverage against the most likely organism in this age group?
Q3: What adjunctive therapy must be given, and crucially, WHEN?
Answers:
1. CSF:serum glucose = 18/90 = 0.20 (i.e., 20% — well below the <40% threshold for bacterial meningitis)
2. Third-generation cephalosporin (ceftriaxone) covers S. pneumoniae and N. meningitidis; add vancomycin given resistance concerns
3. Dexamethasone 0.15 mg/kg IV q6h × 4 days, administered before or with the very first dose of antibiotics
Scenario 2: A 4-day-old neonate has a bulging fontanelle and is not feeding. LP grows a gram-positive bacillus that grows well on blood agar at 4°C.
Q4: What organism is this, and why must you include ampicillin in the regimen?
SELF-CHECK
A 10-year-old boy develops fever, severe headache, and a non-blanching petechial rash spreading over 2 hours. His blood pressure is falling. Before the LP result is back, what is the single most important immediate action?
A. Await CSF culture before starting antibiotics
B. Give IV ceftriaxone immediately and manage shock
C. Give oral rifampicin prophylaxis and observe
D. Obtain urgent CT head and defer antibiotics
Reveal Answer
Answer: B. Give IV ceftriaxone immediately and manage shock
This presentation — fever, non-blanching purpuric rash, and haemodynamic instability — is consistent with meningococcaemia. This is a life-threatening emergency; mortality rises with every hour of antibiotic delay. Ceftriaxone must be given immediately without waiting for LP or CT results. Rifampicin is used for contacts, not treatment. CT is not indicated here as the priority is antibiotic administration and management of septic shock.