What is the recommended treatment for Acute Bacterial Meningitis (ABM) caused by E. Coli?

Treatment of Acute Bacterial Meningitis Caused by E. Coli

For E. coli meningitis, initiate immediate empiric therapy with ceftriaxone 2g IV every 12 hours (or cefotaxime 2g IV every 4-6 hours) plus ampicillin 2g IV every 4 hours, and begin treatment within 1 hour of hospital presentation without waiting for lumbar puncture or imaging if clinically indicated. 1

Age-Specific Treatment Regimens

Neonates (<1 month old)

• Ampicillin/amoxicillin 50 mg/kg every 6-8 hours PLUS cefotaxime 50 mg/kg every 6-8 hours 1
• Alternative: Ampicillin plus an aminoglycoside (gentamicin 2.5 mg/kg every 8-12 hours depending on age) 1
• E. coli is a common pathogen in this age group and requires coverage with both agents 1

Infants (1 month to 18 years)

• Cefotaxime 75 mg/kg every 6-8 hours OR ceftriaxone 50 mg/kg every 12 hours (maximum 2g every 12 hours) 1
• Add vancomycin 10-15 mg/kg every 6 hours if pneumococcal resistance is suspected, though this is less relevant for gram-negative coverage 1

Adults (18-50 years)

• Ceftriaxone 2g IV every 12 hours OR cefotaxime 2g IV every 4-6 hours 1
• Third-generation cephalosporins provide excellent coverage for E. coli and other gram-negative bacilli 2, 3

Adults (>50 years or immunocompromised)

• Ceftriaxone 2g every 12 hours PLUS ampicillin 2g every 4 hours to cover Listeria in addition to gram-negative organisms 1
• This combination is critical as E. coli can occur alongside other pathogens in older adults 1

Treatment Duration

Continue therapy for at least 21 days for aerobic gram-negative bacilli including E. coli 4

• This extended duration is necessary due to the difficulty in eradicating gram-negative organisms from the CNS 4
• For culture-negative cases where E. coli is suspected, maintain empiric treatment for minimum 14 days, extending to 21 days based on clinical response 4

Critical Timing Considerations

Antibiotic administration must occur within 1 hour of hospital arrival 1

• Delayed treatment is strongly associated with death and poor outcomes 1
• Do NOT delay antibiotics for lumbar puncture or CT imaging 1
• Obtain blood cultures before antibiotics, but do not delay treatment for this 1

When to Defer Lumbar Puncture and Start Empiric Treatment Immediately

Start antibiotics BEFORE lumbar puncture if any of the following are present: 1

• Focal neurologic deficits (excluding cranial nerve palsies)
• New-onset seizures
• Severely altered mental status (Glasgow Coma Scale <10)
• Severely immunocompromised state

Alternative Antibiotic Options

Meropenem 2g IV every 8 hours is an effective alternative if third-generation cephalosporins cannot be used 5

• A Swedish registry study showed comparable 30-day mortality between meropenem (3.6%) and cefotaxime plus ampicillin (3.2%) with OR 1.15 (95% CI 0.41-3.22) 5
• However, carbapenems should be reserved for resistant organisms or cephalosporin allergy to preserve their effectiveness 5

Adjunctive Therapy

Dexamethasone is NOT routinely recommended for E. coli meningitis 1, 3

• Corticosteroids show benefit primarily in pneumococcal and H. influenzae meningitis 3, 6
• The evidence for gram-negative meningitis is insufficient to support routine use 1

Avoid routine use of: 1

• Mannitol, hypertonic saline, or glycerol (no proven benefit and may cause harm) 1, 7
• Therapeutic hypothermia (associated with higher mortality) 1
• Prophylactic antiepileptic drugs 1

Fluid Management

Maintain euvolemia with crystalloids as the initial fluid of choice 7

• Target mean arterial pressure ≥65 mmHg to ensure adequate cerebral perfusion 7
• Do NOT restrict fluids in an attempt to reduce cerebral edema, as this worsens outcomes 7

Critical Pitfalls to Avoid

• Never delay antibiotics beyond 1 hour waiting for diagnostic procedures 1
• Do not use rifampicin or fosfomycin as monotherapy due to rapid resistance development 4
• Do not assume imaging is required before treatment - clinical suspicion alone warrants immediate empiric therapy 1
• Do not underdose or shorten duration - gram-negative meningitis requires full 21-day courses 4
• Do not forget ampicillin coverage in older adults (>50 years) to cover Listeria alongside E. coli 1

Monitoring and Follow-up

• Treat seizures early if they occur, as they are associated with worse outcomes and occur in approximately 15% of cases 7
• Consider lumbar drainage for persistently elevated intracranial pressure, not osmotic agents 7
• Intracranial pressure monitoring can be life-saving in selected patients but is not routine 1