What is the protocol-based management of bacterial meningitis?

Protocol-Based Management of Bacterial Meningitis

Immediate Actions (Within 1 Hour of Presentation)

Bacterial meningitis is a neurologic emergency requiring antibiotic administration within 1 hour of hospital arrival, and treatment must never be delayed for imaging or lumbar puncture. 1

Step 1: Stabilization and Blood Cultures

• Assess airway, breathing, and circulation; intubate if Glasgow Coma Scale (GCS) ≤12 or if rapidly evolving purpuric rash with cardiovascular instability is present 1
• Record GCS score on arrival for prognostic information and monitoring 1
• Obtain blood cultures immediately—these are positive in 71% of cases even when CSF culture is negative, especially after antibiotics 2
• Draw blood for procalcitonin, which helps differentiate bacterial from viral meningitis with high sensitivity and specificity 2

Step 2: Decision for CT Scan Before Lumbar Puncture

Perform urgent head CT before lumbar puncture ONLY if any of these high-risk features are present: 3, 1

• Age ≥60 years
• Immunocompromised state (HIV/AIDS, immunosuppressive therapy, transplant)
• History of CNS disease (mass lesion, stroke, focal infection)
• New-onset seizure within past week
• Papilledema on examination
• Altered consciousness or inability to follow commands
• Focal neurological deficits (gaze palsy, facial weakness, limb drift)

If NONE of these criteria are present, proceed directly to lumbar puncture after blood cultures—do not obtain CT. The clinical decision rule has a negative predictive value of 97% for detecting contraindicating intracranial pathology. 1

Critical pediatric exception: Isolated brief seizures should NOT delay lumbar puncture in children, as seizures occur in up to 30% of pediatric bacterial meningitis cases and do not independently indicate raised intracranial pressure. 1

Step 3: Empiric Antibiotic Administration

Start empiric antibiotics immediately after blood cultures, regardless of whether lumbar puncture has been performed. 3, 1

Adults <60 Years Without Immunocompromise:

• Ceftriaxone 2g IV every 12 hours (or cefotaxime 2g IV every 4–6 hours) 1
• PLUS Vancomycin 15–20 mg/kg IV every 8–12 hours (target serum trough 15–20 µg/mL) 1

Adults ≥60 Years OR Immunocompromised:

• Ceftriaxone 2g IV every 12 hours 1
• PLUS Vancomycin 15–20 mg/kg IV every 8–12 hours 1
• PLUS Ampicillin 2g IV every 4 hours (for Listeria monocytogenes coverage) 1, 4

Neonates:

• Ampicillin PLUS cefotaxime 1

Children (≥1 month to <18 years):

• Ceftriaxone or cefotaxime PLUS vancomycin 1

Never use vancomycin alone—it must be combined with a third-generation cephalosporin because CSF penetration can be inadequate, especially when dexamethasone is co-administered. 1

Step 4: Adjunctive Dexamethasone

Administer dexamethasone 10 mg IV every 6 hours for adults (or 0.15 mg/kg IV every 6 hours for children) immediately before or simultaneously with the first antibiotic dose. 1

• Timing is critical: give 10–20 minutes before or with antibiotics; if antibiotics have already begun, dexamethasone can still be started up to 12 hours after the first dose 1
• Continue for 4 days when pneumococcal meningitis is confirmed or highly probable; discontinue if an alternative etiology is identified 1
• Dexamethasone reduces unfavorable outcomes (15% vs 25%; P=0.03) and mortality (7% vs 15%; P=0.04) in adults with bacterial meningitis, with greatest benefit in pneumococcal meningitis (unfavorable outcomes 26% vs 52%; deaths 14% vs 34%) 1

Pediatric exception: Do NOT give dexamethasone to children with meningococcal septicemia (purpuric rash with shock) UNLESS they develop inotrope-resistant shock 1

Lumbar Puncture Timing and Interpretation

When CT Is NOT Indicated:

• Perform lumbar puncture within 1 hour of arrival after blood cultures 1
• Start antibiotics immediately after the lumbar puncture if meningitis is suspected 1

When CT IS Indicated:

• Give antibiotics immediately after blood cultures 1
• Obtain CT scan 1
• Defer lumbar puncture unless CT shows no mass effect or elevated intracranial pressure 1
• Do NOT perform lumbar puncture if CT reveals significant brain swelling, midline shift, or mass lesion 1

If Lumbar Puncture Is Delayed:

• If lumbar puncture cannot be completed within 1 hour, give antibiotics immediately after blood cultures 1
• Perform lumbar puncture as soon as possible, preferably within 4 hours of antibiotic initiation—culture yield falls rapidly after this interval 5
• CSF culture is positive in 73% of patients who have LP up to 4 hours after starting antibiotics, compared with 11% of patients with later LP (p<0.001) 5
• None of the LPs performed more than 8 hours after antibiotics are culture-positive 5

Expected CSF Findings in Bacterial Meningitis:

Parameter	Typical Finding	Clinical Significance
Opening pressure	200–500 mm H₂O	Indicates raised intracranial pressure [1]
WBC count	1,000–5,000 cells/µL (range 100–110,000)	Reflects inflammatory response [1]
Differential	Neutrophils 80–95% (≈10% may be lymphocyte-predominant)	Supports bacterial etiology [1]
Glucose	<40 mg/dL in 50–60% of cases	Bacterial consumption of glucose [1]
CSF/serum glucose ratio	<0.4 in children >12 months; <0.6 in neonates	Distinguishes bacterial from viral meningitis [1]
Protein	Elevated	Blood-brain barrier disruption [1]

Gram Stain Diagnostic Yield:

• Overall sensitivity 60–90% with specificity 97% 1
• Streptococcus pneumoniae: 90% positive 1
• Haemophilus influenzae: 86% positive 1
• Neisseria meningitidis: 75% positive 1
• Gram-negative bacilli: 50% positive 1
• Listeria monocytogenes: 33% positive 1

Fluid Resuscitation and Hemodynamic Support

In patients with septic shock or rapidly evolving rash, prioritize circulatory stabilization with rapid crystalloid boluses and administer antibiotics immediately; lumbar puncture can be deferred until stability is achieved. 1

• Give rapid isotonic fluid boluses of 20 mL/kg (or ≈500 mL in adults), reassessing after each dose, up to a total of 60 mL/kg 1
• Maintain mean arterial pressure ≥65 mm Hg to ensure adequate cerebral perfusion 1
• Patients requiring >60 mL/kg often need inotropic support; consider early ventilatory support once inotropes are started for fluid-resistant shock 1
• For inotrope-resistant shock, add intravenous vasopressin and titrate steroid dosing 1

ICU Transfer Criteria

Transfer to intensive care when any of the following are present: 1

• Rapidly evolving purpuric rash
• GCS ≤12
• Cardiovascular instability or hypoxia requiring monitoring or organ support
• National Early Warning Score ≥7 (or ≥5 with a single parameter score of 3)

Management of Partially Treated Bacterial Meningitis

If antibiotics were given before lumbar puncture, CSF analysis remains helpful and should still be performed. 6

Diagnostic Considerations:

• CSF Gram stain sensitivity decreases by approximately 20% (from 60–90% to lower rates) 6
• CSF cultures may be sterilized within 2 hours for meningococci and within 4 hours for pneumococci after antibiotic administration 6
• Despite reduced culture yield, CSF findings (elevated WBC, diminished glucose, elevated protein) will likely provide evidence for or against bacterial meningitis 6
• CSF profile may show lymphocyte predominance rather than typical neutrophil predominance if antibiotics were given before lumbar puncture 6

Molecular Diagnostics:

• CSF PCR should be utilized—it has sensitivity of 87–100% and specificity of 98–100%, and remains positive even after antibiotics 6
• If organism-specific PCR is negative, 16S ribosomal RNA PCR can detect most bacteria 6
• Multiplex PCR platforms that detect multiple pathogens simultaneously can reduce diagnostic time and increase sensitivity 6

Management Approach:

• Do NOT assume viral meningitis based solely on lymphocytic predominance in CSF, as partially treated bacterial meningitis can present with lymphocyte predominance 6
• Do NOT discontinue antibiotics based on negative CSF cultures alone if clinical presentation and CSF parameters (elevated WBC, low glucose, high protein) are consistent with bacterial meningitis and the patient received antibiotics before lumbar puncture 6
• Continue empiric therapy with vancomycin plus ceftriaxone/cefotaxime pending culture results 6

Definitive Antibiotic Therapy (Once Organism Identified)

Duration by Pathogen:

• Streptococcus pneumoniae: 10–14 days 1, 2
• Neisseria meningitidis: 5–7 days 1, 2
• Unknown pathogen with satisfactory clinical progress: minimum 7–10 days 1
• Minimum treatment duration: 48–72 hours beyond clinical improvement or bacterial eradication 2

Chemoprophylaxis for Close Contacts (Meningococcal Disease):

• Offer antimicrobial prophylaxis to individuals with prolonged close household exposure during the 7 days preceding the index case's onset 1
• Defined close contacts include household members, dormitory residents, intimate partners, and university students sharing a kitchen 1
• Effective prophylactic agents: ciprofloxacin 500 mg PO single dose, rifampicin, minocycline, or ampicillin 1

Critical Pitfalls to Avoid

1. Never delay antibiotics for imaging or lumbar puncture—treatment must begin within 1 hour of presentation 3, 1
2. Never use vancomycin alone—it must be combined with a third-generation cephalosporin 1
3. Never omit ampicillin in adults ≥60 years or immunocompromised patients—Listeria coverage is essential 1
4. Never administer dexamethasone more than 12 hours after the first antibiotic dose—timing is critical for benefit 1
5. Never assume normal CSF at initial LP excludes bacterial meningitis—meningitis can present with minimal or absent pleocytosis, especially early in illness, and mortality in such cases is high 2, 7
6. Never rely solely on latex agglutination tests—they have been largely surpassed by PCR 6
7. Never send patients for unnecessary CT scans—only 20 of 62 patients (32%) who received CT scans in one study had a contraindication to immediate LP 5

Follow-Up and Monitoring

• Hearing assessment should be performed during admission and repeated if abnormal 2
• Monitor for complications: hearing loss (most common neurological sequela), psychiatric/psychosocial/behavioral problems, renal impairment, and post-traumatic stress disorder 1
• Consider outpatient IV antibiotic therapy (OPAT) if patient is afebrile, clinically improving, and has reliable IV access 1