What is the recommended initial management of suspected acute bacterial meningitis, including diagnostics, empiric antimicrobial therapy, steroids, and supportive care?

Initial Management of Suspected Acute Bacterial Meningitis

In suspected acute bacterial meningitis, immediately obtain blood cultures and administer empiric antibiotics within 1 hour of hospital arrival—do not delay treatment for imaging or lumbar puncture, as every hour of delay increases mortality and neurological morbidity. 1, 2

Immediate Stabilization and Assessment (First Hour)

Stabilize airway, breathing, and circulation as the absolute first priority. 1

• Document Glasgow Coma Scale score immediately upon arrival for prognostic assessment and to monitor deterioration 1, 3
• Assess for signs of shock: capillary refill >2 seconds, hypotension (mean arterial pressure <65 mmHg), altered mental status, or lactate >2 mmol/L 1
• If shock or rapidly evolving purpuric rash is present, initiate aggressive fluid resuscitation with 500 mL crystalloid bolus immediately and do NOT perform lumbar puncture at this time 1
• Involve intensive care teams immediately if GCS ≤12, cardiovascular instability, hypoxia, or rapidly evolving rash is present 2

Diagnostic Algorithm

Blood Cultures First

Obtain blood cultures within 1 hour of arrival before any antibiotics are given—blood cultures are positive in 71% of cases even when CSF cultures fail, making them critical for diagnosis. 1, 4

Decision Point: CT Scan Before Lumbar Puncture?

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

• Immunocompromised state (HIV, immunosuppressive drugs, malignancy)
• History of CNS disease (mass lesion, stroke, focal infection)
• New-onset seizure within the past week
• Altered consciousness or inability to follow commands
• Focal neurological deficits (gaze palsy, facial weakness, limb drift, aphasia)
• Papilledema on fundoscopic examination
• GCS ≤12

If NONE of these features are present, proceed directly to lumbar puncture without CT imaging. 1, 2

Lumbar Puncture Timing

In patients without shock or severe sepsis: 1

• Perform LP within 1 hour of arrival if no CT contraindications exist
• Start antibiotics immediately after LP is completed, within the first hour
• If LP cannot be performed within 1 hour, start antibiotics immediately after blood cultures and perform LP as soon as possible thereafter—preferably within 4 hours of antibiotic initiation 1, 5

Critical timing evidence: CSF culture positivity drops dramatically after antibiotics—73% positive if LP done within 4 hours versus only 11% if delayed beyond 4 hours, and zero positivity after 8 hours. 5

In patients with shock, severe sepsis, or rapidly evolving rash: 1

• Give antibiotics immediately after blood cultures
• Do NOT perform LP during acute resuscitation phase
• Defer LP until patient is stabilized

Empiric Antimicrobial Therapy

Standard Adult Regimen (<60 years, immunocompetent)

Administer the following combination immediately: 2, 3

• Ceftriaxone 2g IV every 12 hours OR Cefotaxime 2g IV every 6 hours
• PLUS Vancomycin 15-20 mg/kg IV every 8-12 hours (target serum trough 15-20 µg/mL)

Never use vancomycin alone—it must be combined with a third-generation cephalosporin due to inadequate CSF penetration, especially when dexamethasone is co-administered. 2

Modified Regimen for High-Risk Patients (≥60 years or immunocompromised)

Add Ampicillin 2g IV every 4 hours to the above regimen for Listeria monocytogenes coverage. 2, 3

Risk factors mandating Listeria coverage include: 2

• Age >50-60 years
• Diabetes mellitus
• Immunosuppressive therapy
• Malignancy
• Other immunocompromising conditions

Pediatric Regimens

Neonates (<3 months): 1, 2

• Cefotaxime PLUS Ampicillin (or Amoxicillin)
• Do NOT use ceftriaxone in neonates due to risk of fatal calcium-ceftriaxone precipitation 1

Children (≥3 months): 1, 2

• Cefotaxime or Ceftriaxone PLUS Vancomycin

Adjunctive Dexamethasone Therapy

Administer dexamethasone 10 mg IV every 6 hours (or 0.15 mg/kg in children) immediately before or simultaneously with the first antibiotic dose—this reduces mortality from 15% to 7% and unfavorable outcomes from 25% to 15% in adults. 2

Critical timing requirements: 2

• Give 10-20 minutes before antibiotics or at the same time
• Can still be given up to 12 hours after first antibiotic dose, but benefit diminishes
• Never give dexamethasone more than 12 hours after antibiotics—timing is critical for efficacy

Duration: 1, 2

• Continue for 4 days if pneumococcal meningitis is confirmed or highly probable
• Discontinue if alternative etiology (viral, fungal) is identified
• In children with meningococcal meningitis, continue full 4-day course 1

Special consideration with vancomycin: Dexamethasone reduces vancomycin CSF penetration, so consider adding Rifampin 300 mg IV every 12 hours to the regimen in suspected pneumococcal meningitis. 2

Exception—do NOT use dexamethasone: In children with meningococcal septicaemia (shock without meningitis), steroids are not recommended except for inotrope-resistant shock. 1

CSF Interpretation

Expected Findings in Bacterial Meningitis 1, 4

Parameter	Typical Finding	Clinical Significance
Opening pressure	200-500 mm H₂O	Indicates raised ICP
WBC count	1,000-5,000 cells/mm³ (range 100-110,000)	Elevated in virtually all cases
Differential	80-95% neutrophils	~10% may show lymphocyte predominance
Glucose	<40 mg/dL in 50-60%	Hypoglycorrhachia strongly suggests bacterial etiology
CSF/serum glucose ratio	<0.4 (children >12 months); <0.6 (neonates)	80% sensitive, 98% specific
Protein	Elevated	Marker of blood-brain barrier disruption

Gram Stain Diagnostic Yield 1, 4

Overall sensitivity: 60-90% in untreated patients, but drops ~20% if antibiotics given before LP 4

Pathogen-specific positivity rates: 1

• Streptococcus pneumoniae: 90%
• Haemophilus influenzae: 86%
• Neisseria meningitidis: 75%
• Gram-negative bacilli: 50%
• Listeria monocytogenes: 33%

Partially Treated Meningitis

If antibiotics were given before LP, CSF findings remain diagnostically useful: 4

• Elevated WBC, low glucose, and high protein persist despite antibiotic pretreatment
• Order CSF PCR (sensitivity 87-100%, specificity 98-100%)—remains positive even after antibiotics 4
• Blood cultures obtained before antibiotics may be positive even when CSF cultures are negative 4
• Never assume viral meningitis based solely on lymphocyte predominance in CSF—partially treated bacterial meningitis can present this way 4

Supportive Care

Fluid Management

Maintain euvolemic state to preserve normal hemodynamic parameters—do NOT restrict fluids to reduce cerebral edema. 3

In shock: 1

• Administer rapid 500 mL crystalloid boluses (20 mL/kg in children)
• Reassess after each bolus; may require up to 60 mL/kg total
• Use norepinephrine as first-line vasopressor if fluid-resistant shock develops, targeting mean arterial pressure ≥65 mmHg 3

Seizure Management

If continuous or uncontrolled seizures occur, this is a contraindication to immediate LP and requires urgent neuroimaging. 1

ICU Transfer Criteria 2

Transfer to intensive care if:

• GCS ≤12
• Rapidly evolving purpuric rash
• Cardiovascular instability requiring inotropes
• Respiratory failure requiring ventilatory support
• Inotrope-resistant shock (consider vasopressin and stress-dose steroids as rescue)

Common Pitfalls to Avoid

Never delay antibiotics for imaging or LP—treatment must begin within 1 hour regardless of diagnostic testing status. 1, 2

Never send patients for unnecessary CT scans—67% of delays in one study were due to CT scans in patients without contraindications to immediate LP. 5

Never use vancomycin monotherapy—it must be combined with ceftriaxone or cefotaxime. 2

Never omit Listeria coverage in patients ≥50-60 years or immunocompromised—add ampicillin to the empiric regimen. 2

Never use ceftazidime as empiric therapy for community-acquired meningitis—it has inferior pneumococcal coverage and should be reserved for nosocomial or Pseudomonas infections. 2

Never rely solely on negative CSF cultures to exclude bacterial meningitis if antibiotics were given before LP—use clinical parameters, CSF chemistry, and PCR testing. 4

Never assume absence of pleocytosis excludes meningitis—rare cases (124 reported) of culture-proven bacterial meningitis occur without CSF pleocytosis, with 31% mortality; blood cultures are positive in 71% of these cases. 6

Never discontinue empiric therapy based on initial negative Gram stain alone—Gram stain sensitivity is only 60-90% and varies by pathogen. 1, 4