Fellow's quick read · Infectious Diseases
Bacterial meningitis
IDSA 2004 (Tunkel) · local our institution CNS CPG 2020 · reviewed 2026-06-20
Personal study digest for a new ID fellow. Recommendations are drawn from the IDSA 2004 bacterial meningitis guideline and our CNS Infections CPG (2020). The “What’s changed since 2004” section is reviewer synthesis of newer evidence, each claim cited. Not a substitute for the full guideline.
In one line
Acute bacterial meningitis is a true emergency — the entire fellow game is to compress door-to-antibiotic time: draw blood cultures, give dexamethasone + empiric antibiotics without waiting for CT or LP, then tailor. Vancomycin + ceftriaxone is the adult backbone; add ampicillin once age >50 or immunocompromised (Listeria).◆When to suspect / diagnose
- The classic triad (fever, neck stiffness, altered mentation) is present in a minority; nearly all have fever plus at least one of headache, neck stiffness, or altered mental status. A petechial/purpuric rash points to meningococcus.
- LP for CSF: cell count + differential, glucose, protein, Gram stain, culture, and the multiplex meningitis/encephalitis PCR panel. Measure the opening pressure. Always send blood cultures too.
- CT head BEFORE LP only if (IDSA 2004, B-II): immunocompromised, history of CNS disease (mass/stroke), new-onset seizure (<1 wk), papilledema, abnormal level of consciousness, or focal neurologic deficit. Otherwise LP without delay — and never delay antibiotics for it.
◆Workup the fellow drives
- Antibiotics + dexamethasone first, imaging second. If LP is deferred for CT, draw blood cultures and start empiric therapy immediately (target <1 h; local CPG says ideally within 30 min).
- Dexamethasone 0.15 mg/kg IV q6h — first dose 10–20 min BEFORE (or with) the first antibiotic dose. Do not start it once antibiotics have already been given; it won’t help.
- The multiplex CSF PCR speeds the answer (~1 h) but does not replace culture (needed for susceptibilities) and a negative panel does not exclude HSV or Cryptococcus.
- Infectious Diseases consult on every case. Repeat LP if no clinical response, worsening, or resistant pneumococcus on dexamethasone.
◆Empiric & definitive therapy
| Scenario | Drug / dose / route | Notes |
|---|---|---|
| Empiric 2–50 y, immunocompetent | Vancomycin (AUC/trough-guided, target trough 15–20) + ceftriaxone 2 g IV q12h | Covers S. pneumoniae + N. meningitidis |
| Empiric >50 y or immunocompromised | Add ampicillin 2 g IV q4h (immunocompromised: use cefepime in place of ceftriaxone) | Adds Listeria cover (and Pseudomonas/GNB if immunocompromised) |
| Post-neurosurgery / penetrating trauma / shunt | Vancomycin + cefepime 2 g q8h (or meropenem 2 g q8h) | Covers staphylococci + Pseudomonas/GNB |
| Adjunctive dexamethasone | 0.15 mg/kg IV q6h ×2–4 d, before/with 1st antibiotic | Continue ONLY if S. pneumoniae; stop for any other organism |
| If HSV cannot be excluded | Add acyclovir 10 mg/kg IV q8h | Empiric until HSV encephalitis ruled out (local CPG) |
- Definitive (de-escalate by pathogen + MIC): S. pneumoniae → ceftriaxone, add vancomycin if ceftriaxone MIC ≥1; N. meningitidis → ceftriaxone (pen G if susceptible); Listeria → ampicillin + gentamicin; H. influenzae → ceftriaxone; P. aeruginosa → cefepime or meropenem.
- Severe β-lactam allergy: moxifloxacin (pneumococcus/meningococcus) ± TMP-SMX (Listeria); verify the allergy and consider de-labeling.
◆Duration & stopping
- N. meningitidis & H. influenzae: 7 days.
- S. pneumoniae: 10–14 days.
- S. agalactiae (GBS): 14–21 days · aerobic Gram-negative bacilli: 21 days · Listeria: ≥21 days.
- Durations are A-III (expert opinion / tradition), not RCT-derived — clinical course and source still matter.
◆Key decisions a fellow owns
- Do not delay antibiotics for CT or LP — the single highest-impact move.
- Get dexamethasone in before/with the first dose, and stop it if the organism isn’t pneumococcus.
- Apply the CT-before-LP criteria deliberately; don’t reflexively scan everyone.
- Do NOT induce therapeutic hypothermia (see below).
What’s changed since 2004
Reviewer synthesis of newer evidence — not the guideline. Each claim cited; flags where the 2004 IDSA guideline lags current practice.
- Still no newer IDSA community-acquired meningitis guideline — the 2004 Tunkel document remains the operative US reference. The 2017 IDSA guideline covers healthcare-associated ventriculitis/meningitis (different scope); Europe’s ESCMID 2016 and now WHO 2025 fill the gap. IDSA: CID 2004;39:1267 · ESCMID: Clin Microbiol Infect 2016;22(S3):S37–62
- First-ever WHO global meningitis guideline (Nov 2025) — corticosteroids with the first antibiotic dose in suspected bacterial meningitis, stop if CSF isn’t consistent with bacterial; not routinely during meningococcal epidemics; and empiric antibiotics may be stopped at 7 days if the pathogen is unknown and the patient has recovered (a resource-variable framing — US practice still favors pathogen-specific durations). WHO guidelines on meningitis diagnosis, treatment and care, 2025
- Induced hypothermia is HARMFUL — do not cool. Multicenter RCT in 98 comatose adults (77% pneumococcal) stopped early for excess mortality: 51% vs 31% (RR 1.99, 95% CI 1.05–3.77). Mourvillier, JAMA 2013;310:2174–83 (PMID 24105303)
- Dexamethasone — confirmed, with refined indication. Cochrane 2015 (25 RCTs, n=4121): reduces hearing loss and neurologic sequelae; mortality benefit only in S. pneumoniae (RR 0.84) and only in high-income countries — no overall mortality benefit, none in low-income settings. Brouwer/van de Beek, Cochrane 2015, CD004405 (PMID 26362566)
- Multiplex CSF PCR (BioFire ME panel) — new diagnostic the 2004 text predates. ~90% sensitivity / 97% specificity; a negative panel does NOT exclude HSV or Cryptococcus (highest false-negatives), and false positives are highest for S. pneumoniae — it complements but does not replace culture/CrAg/HSV PCR. Tansarli & Chapin, Clin Microbiol Infect 2020;26:281–90
- Listeria — ampicillin + gentamicin supported; avoid steroids. Largest prospective cohort backs the β-lactam + aminoglycoside combination and links adjunctive dexamethasone to worse outcomes in confirmed listeriosis. MONALISA, Charlier, Lancet Infect Dis 2017;17:510–19 (PMID 28139432)
- Vaccine-driven epidemiology has shifted the bugs. PCV13→PCV15/20, conjugate Hib and meningococcal vaccines reduced disease and shifted serotypes — but the empiric regimen above is unchanged. reviewer synthesis
◆Anki cards minted this run
- Induced hypothermia is harmful in severe bacterial meningitis (Mourvillier, JAMA 2013).
- Dexamethasone reduces sequelae, but mortality benefit only in pneumococcus + high-income settings (Cochrane 2015).
- A negative FilmArray ME panel does not exclude HSV or Cryptococcus.
- Stop/avoid adjunctive dexamethasone once Listeria is confirmed (MONALISA).
- Held (cap 4 / already in deck): empiric vanc+ceftriaxone regimen, “add ampicillin once age >50,” “give dexamethasone before the first dose for pneumococcus,” and “Listeria = ampicillin + gentamicin” — all already carded; WHO-2025 7-day empiric-stop rule held as resource-variable.
Sources: IDSA bacterial meningitis guideline (Tunkel, Clin Infect Dis 2004;39:1267–1284, doi:10.1086/425368); WHO guidelines on meningitis diagnosis, treatment and care (2025); ESCMID guideline (van de Beek, Clin Microbiol Infect 2016;22 Suppl 3:S37–62); induced hypothermia RCT (Mourvillier, JAMA 2013;310:2174–83, PMID 24105303); corticosteroids Cochrane review (Brouwer/van de Beek 2015, CD004405, PMID 26362566); FilmArray ME panel meta-analysis (Tansarli & Chapin, Clin Microbiol Infect 2020;26:281–290); MONALISA listeriosis cohort (Charlier, Lancet Infect Dis 2017;17:510–519, PMID 28139432); our institution CNS Infections in Adults CPG (2020).