What is the recommended initial assessment and empiric treatment for a patient with suspected bacterial meningitis, including adults, children, and special populations such as the elderly, immunocompromised, pregnant patients, and infants?

Approach to Suspected Bacterial Meningitis

Administer empiric antibiotics within 1 hour of presentation—immediately after obtaining blood cultures—and do not delay treatment for imaging or lumbar puncture. 1, 2

Immediate Stabilization (First 15 Minutes)

• Assess airway, breathing, and circulation as the immediate priority; intubate if Glasgow Coma Scale (GCS) ≤12 or if the patient has rapidly evolving rash with cardiovascular instability. 1, 2
• Document GCS score for prognostic value and to monitor deterioration. 1, 3
• Obtain blood cultures immediately within the first hour, before any antibiotics are given. 1, 2
• Record presence or absence of petechial/purpuric rash, which is highly indicative of meningococcal infection (>90% of cases when present). 3

Decision: CT Before Lumbar Puncture?

Perform urgent head CT before lumbar puncture only if any of the following high-risk features are present: 1, 2

• Age ≥60 years
• Immunocompromised state (HIV/AIDS, immunosuppressive therapy, transplant, malignancy)
• History of CNS disease (mass lesion, stroke, focal infection)
• New-onset seizure within the past week
• Altered mental status (inability to answer 2 consecutive questions or follow 2 consecutive commands)
• Focal neurological deficits (gaze palsy, visual field defect, facial palsy, arm/leg drift, abnormal language)
• Papilledema
• GCS ≤12
• Continuous or uncontrolled seizures

If none of these criteria are present, proceed directly to lumbar puncture after blood cultures—do not obtain CT. 1, 2 The negative predictive value of this clinical decision rule is 97%. 1

Critical Pitfall to Avoid

Brief seizures alone should not delay lumbar puncture in children, as seizures occur in up to 30% of pediatric bacterial meningitis cases before admission and do not independently indicate elevated intracranial pressure. 1, 2

Empiric Antibiotic Therapy (Start Within 1 Hour)

Adults <50 Years (Immunocompetent)

Ceftriaxone 2g IV every 12 hours (or cefotaxime 2g IV every 4–6 hours) PLUS vancomycin 15–20 mg/kg IV every 8–12 hours (target trough 15–20 µg/mL). 2, 4

Adults ≥50 Years OR Immunocompromised

Add ampicillin 2g IV every 4 hours to the above regimen for Listeria monocytogenes coverage. 2, 4 Risk factors for Listeria include age >50, diabetes, immunosuppressive drugs, cancer, and other immunocompromising conditions. 2

Neonates (<1 Month)

Ampicillin 2g IV every 4 hours PLUS cefotaxime 2g IV every 6 hours (avoid ceftriaxone in neonates due to bilirubin displacement). 2, 5

Children (1 Month to 18 Years)

Cefotaxime 2g IV every 6 hours (or ceftriaxone 2g IV every 12 hours) PLUS vancomycin 15–20 mg/kg IV every 8–12 hours. 1, 2

Pregnant Patients

Ceftriaxone 2g IV every 12 hours PLUS ampicillin 2g IV every 4 hours (for Listeria coverage, as pregnancy is an immunocompromised state). 2

Critical Pitfalls to Avoid

• Never use vancomycin monotherapy—it must be combined with a third-generation cephalosporin due to inadequate CSF penetration. 2
• Never use ceftazidime as empiric therapy for community-acquired meningitis; reserve it for nosocomial or post-neurosurgical cases with Pseudomonas risk. 2
• Never use tobramycin or other aminoglycosides as primary therapy—they do not achieve adequate CSF penetration. 4

Adjunctive Dexamethasone Therapy

Administer dexamethasone 10 mg IV every 6 hours (or 0.15 mg/kg IV every 6 hours in children) immediately before or simultaneously with the first antibiotic dose. 2, 4

• Timing is critical: Dexamethasone must be given within 10–20 minutes before or with the first antibiotic dose; if antibiotics have already started, it can still be given up to 4–12 hours later, but benefit diminishes. 2
• Continue for 4 days if pneumococcal meningitis is confirmed or highly probable; discontinue if an alternative etiology is identified. 2
• Clinical benefit: Reduces unfavorable outcomes (15% vs 25%; P=0.03) and mortality (7% vs 15%; P=0.04) in adults, with greatest effect in pneumococcal meningitis (deaths 14% vs 34%). 2
• In children: Reduces mortality and hearing loss in Streptococcus pneumoniae and Haemophilus influenzae meningitis. 2

Exception: Meningococcal Septicemia

Do not give dexamethasone in children with meningococcal septicemia (purpuric rash with shock) unless inotrope-resistant shock develops. 1, 2

Interaction with Vancomycin

Dexamethasone may lower vancomycin CSF penetration; compensate by targeting higher serum troughs (15–20 µg/mL) or consider adding rifampin 300 mg IV every 12 hours in suspected pneumococcal meningitis. 2

Timing of Lumbar Puncture

If No CT Indications Present

Perform lumbar puncture within 1 hour of arrival, immediately after blood cultures are obtained. 1, 2

• Start antibiotics immediately after LP if meningitis is suspected. 1
• If LP cannot be performed within 1 hour, start antibiotics after blood cultures and perform LP as soon as possible thereafter—preferably within 4 hours of starting antibiotics, as culture yield drops rapidly after that. 1

If CT Indications Present

Start antibiotics immediately after blood cultures, then obtain CT. 1, 2

• Perform LP after CT only if no mass effect or elevated intracranial pressure is seen. 2
• Do not perform LP if CT shows significant brain swelling, midline shift, or mass lesion. 1

Patients with Septic Shock or Rapidly Evolving Rash

Do not perform LP at initial presentation; prioritize circulatory stabilization with fluid resuscitation (500 mL crystalloid bolus, up to 60 mL/kg in children) and immediate antibiotics. 1 LP may be considered later if diagnostic uncertainty persists and there are no contraindications (coagulopathy, low platelets, cardiovascular instability, neurological concerns). 1

Expected CSF Findings in Bacterial Meningitis

Parameter	Typical Finding	Clinical Significance
Opening pressure	200–500 mm H₂O	Indicates raised intracranial pressure [2]
WBC count	1,000–5,000 cells/µL (range 100–110,000)	Reflects intense inflammation [2]
Differential	Neutrophils 80–95% (≈10% may be lymphocyte-predominant)	Supports bacterial etiology [2]
Glucose	<40 mg/dL in 50–60% of cases	Bacterial consumption of glucose [2]
CSF/serum glucose ratio	<0.4 in children >12 months; <0.6 in neonates	Distinguishes bacterial from viral meningitis [2]
Protein	Elevated (typically >100 mg/dL)	Blood-brain barrier disruption [2]
Gram stain sensitivity	60–90% overall; 90% for S. pneumoniae, 75% for N. meningitidis, 33% for Listeria	Rapid organism identification [2]

Fluid Management and Hemodynamic Support

Maintain euvolemia with crystalloid fluids—do not restrict fluids in an attempt to reduce cerebral edema, as this is explicitly contraindicated in meningitis. 4

• If shock is present, give rapid 500 mL crystalloid boluses (20 mL/kg in children), reassessing after each dose, up to 60 mL/kg total. 1
• Patients requiring >60 mL/kg often need inotropic support; consult intensive care early. 1, 2
• Maintain mean arterial pressure ≥65 mmHg to ensure adequate cerebral perfusion. 4

Intensive Care Transfer Criteria

Transfer to ICU if any of the following are present: 2

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

Duration of Antibiotic Therapy

Continue empiric therapy for 7–10 days if the pathogen is unknown and clinical progress is satisfactory. 2 Once culture results are available:

• Streptococcus pneumoniae: 10 days 2
• Neisseria meningitidis: 5 days 2
• Listeria monocytogenes: 21 days 2

Chemoprophylaxis for Close Contacts

Offer antimicrobial prophylaxis to household members, dormitory residents, intimate partners, and others with prolonged close exposure during the 7 days preceding onset if Neisseria meningitidis is confirmed. 2 Effective agents include ciprofloxacin 500 mg PO single dose, rifampicin, or minocycline. 2

Common Pitfalls Summary

• Never delay antibiotics for imaging or LP—treatment must begin within 1 hour. 1, 2
• Never omit vancomycin from the empiric regimen when resistant pneumococcal strains are a concern. 2
• Never fail to add ampicillin in patients ≥50 years or immunocompromised (Listeria coverage). 2, 4
• Never give dexamethasone >12 hours after the first antibiotic dose—timing is critical. 2
• Never restrict fluids in meningitis; maintain euvolemia. 4