What is the recommended treatment for a patient diagnosed with Streptococcus agalactiae (Group B streptococcal) meningitis?

Treatment of Streptococcus agalactiae (Group B Streptococcal) Meningitis

For neonates less than 1 month old with S. agalactiae meningitis, treat with ampicillin/amoxicillin 50 mg/kg every 6-8 hours plus cefotaxime 50 mg/kg every 6-8 hours intravenously, and for adults and children over 1 month, treat with ceftriaxone 2 grams IV every 12 hours (or cefotaxime 2 grams IV every 4-6 hours) for 10-14 days. 1, 2

Age-Based Treatment Algorithm

Neonates (<1 month old)

Primary regimen:

• Age <1 week: Ampicillin 50 mg/kg IV every 8 hours PLUS cefotaxime 50 mg/kg IV every 8 hours 1
• Age 1-4 weeks: Ampicillin 50 mg/kg IV every 6 hours PLUS cefotaxime 50 mg/kg IV every 6-8 hours 1

Alternative regimen (if cephalosporin unavailable):

• Ampicillin 50 mg/kg IV every 6-8 hours PLUS gentamicin 2.5 mg/kg IV every 8-12 hours (based on age) 1

Critical caveat: The FDA label explicitly indicates ampicillin for bacterial meningitis caused by Group B Streptococci, and recommends 150-200 mg/kg/day in equally divided doses every 3-4 hours for bacterial meningitis in neonates, which differs from the ESCMID guideline dosing 2. The higher FDA-recommended dosing should be considered for severe cases.

Children (1 month to 18 years)

• Ceftriaxone 50 mg/kg IV every 12 hours (maximum 2 grams every 12 hours) 1
• OR cefotaxime 75 mg/kg IV every 6-8 hours 1

Adults (18-50 years)

• Ceftriaxone 2 grams IV every 12 hours 1, 3
• OR cefotaxime 2 grams IV every 4-6 hours 1

Adults (>50 years or immunocompromised)

• Ceftriaxone 2 grams IV every 12 hours PLUS ampicillin 2 grams IV every 4 hours (to cover potential Listeria monocytogenes co-infection) 1, 4
• OR cefotaxime 2 grams IV every 4-6 hours PLUS ampicillin 2 grams IV every 4 hours 1

Treatment Duration

• Standard duration: 10-14 days 1, 3
• 10 days is adequate if the patient has clinically recovered by day 10 (afebrile, improved mental status, decreased neck stiffness) 3, 4
• Extend to 14 days if clinical response is delayed or if the patient has not fully recovered by day 10 3, 4
• Minimum 48-72 hours beyond clinical improvement and evidence of bacterial eradication 2

Critical Timing Considerations

Antibiotic administration must begin within 1 hour of hospital presentation 1. If lumbar puncture is delayed due to:

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

Then start empiric antibiotics immediately after drawing blood cultures, even before LP is performed 1. Delayed antibiotic treatment is strongly associated with death and poor outcome 1.

Adjunctive Therapy Considerations

While the guidelines focus on pneumococcal meningitis, dexamethasone use in S. agalactiae meningitis is not well-established 5. One case report describes successful treatment with dexamethasone, vancomycin, and ceftriaxone, but this represents off-guideline use 5.

Special Clinical Scenarios

For patients with high-level gentamicin resistance (HLGR): Avoid aminoglycoside combination therapy, as HLGR abrogates the synergistic bactericidal activity of penicillin plus gentamicin 6. This is particularly relevant for hypervirulent serotype IV ST1010 strains, which show increasing prevalence of HLGR 6.

For patients with CSF fistula or anatomic defects: S. agalactiae meningitis can occur as a complication of chronic CSF leakage 7. Surgical repair of the fistula should be considered after antimicrobial treatment to prevent recurrence 7.

For late-onset neonatal disease: Nosocomial cross-infection is an important source in late-onset GBS meningitis (>7 days of age), distinct from early-onset disease which originates from maternal colonization 8.

Common Pitfalls to Avoid

1. Do not use vancomycin routinely for S. agalactiae meningitis unless there is documented resistance to beta-lactams, as S. agalactiae remains universally susceptible to penicillins and cephalosporins 5, 9

2. Do not use once-daily ceftriaxone dosing for meningitis - twice-daily dosing (every 12 hours) is essential to maintain adequate CSF concentrations throughout the dosing interval 3, 4

3. Do not stop antibiotics prematurely - complete the full 10-14 day course even if the patient appears clinically improved earlier 3, 2

4. Do not use bacteriostatic water for injection as a diluent in newborns when reconstituting ampicillin 2

5. Avoid rapid IV administration of ampicillin - administer slowly over at least 10-15 minutes for doses ≥1 gram to prevent convulsive seizures 2