Sequential management of bacterial meningitis

1. Blood cx, initiate empiric antibiotics, consider corticosteroids (vide infra)
2. CT head if indicated (see below)
3. LP ASAP (if not contraindicated); yield of CSF cx unlikely to be changed if obtained w/in ~4 h of initiation of abx

Diagnostic studies (NEJM 2017;388:3036)

• Blood cultures ×2 before abx
• WBC count: >10,000 in >90% of bacterial meningitis in healthy hosts
• Head CT to r/o mass effect before LP if ≥1 high-risk feature: immunosupp., h/o CNS disease, new-onset seizure, focal neuro findings, papilledema, GCS <15 (CID 2004;39:1267)
• Lumbar puncture with opening pressure (NEJM 2006;355:e12) Send CSF for cell count and differential, glucose, protein, Gram stain, bacterial cx Additional CSF studies based on clinical suspicion: AFB smear/cx (or MTb PCR), cryptococcal Ag, fungal cx, VDRL, PCR (HSV, VZV, enteroviral), cytology CSF Gram stain has 30–90% Se; cx 80–90% Se if LP done prior to abx though abx should not be delayed for LP if there is concern for bacterial meningitis Rule of 2s: CSF WBC >2k, gluc <20, TP >200 has >98% Sp for bacterial meningitis Repeat LP only if no clinical response after 48 h of appropriate abx or CSF shunt Metagenomic next-generation sequencing ↑ dx yield (NEJM 2019;380:2327)