What is the treatment for bacterial meningitis caused by Streptococcus equisimilis (Group C or G streptococcus) in cerebrospinal fluid (CSF)?

Treatment of Streptococcus equisimilis (Group C/G Streptococcus) Meningitis

For bacterial meningitis caused by Streptococcus equisimilis confirmed by CSF culture, treat with high-dose intravenous penicillin G (24 million units/day divided every 4 hours) or ceftriaxone (2g IV every 12 hours) for 10-14 days, with adjunctive dexamethasone administered before or with the first antibiotic dose.

Immediate Management Approach

Initial Antibiotic Therapy

• Antibiotic therapy must be initiated within 1 hour of presentation, as delay is strongly associated with increased mortality and poor neurological outcomes 1, 2
• Blood cultures should be obtained before antibiotics, but antibiotic administration must not be delayed 3, 1
• If the organism is already identified as Streptococcus equisimilis (Group C or G streptococcus), targeted therapy can be initiated immediately 3

Targeted Antibiotic Selection for S. equisimilis

First-line options:

• Penicillin G 24 million units/day IV, administered as 2-4 million units every 4 hours 4
  • Group C and G streptococci remain highly susceptible to penicillin 4
  • Penicillin G achieves excellent CSF penetration with inflamed meninges (CSF/serum ratio of 2-6%) 4
  • This is the preferred agent given the organism's consistent penicillin susceptibility

Alternative option:

• Ceftriaxone 2g IV every 12 hours 3, 1, 2
  • Provides excellent CSF penetration and bactericidal activity 5
  • Appropriate if penicillin allergy or resistance concerns exist
  • Can be transitioned to once-daily dosing after the first 24 hours if clinical improvement occurs 3

Adjunctive Corticosteroid Therapy

• Dexamethasone 10mg IV every 6 hours should be administered immediately before or simultaneously with the first antibiotic dose 1, 2
• Continue for 4 days total 1
• This reduces mortality and neurological morbidity, particularly in streptococcal meningitis 2

Treatment Duration

The recommended duration for streptococcal meningitis is 10-14 days 3, 1:

• If the patient has clinically recovered by day 10, antibiotics can be safely discontinued 3
• For complicated cases or slow clinical response, extend to 14 days 6
• Clinical recovery is defined as: afebrile status, improving mental status, and resolving meningeal signs 3

Monitoring and Clinical Response Assessment

Day 2-3 Assessment

• Evaluate clinical response: fever curve, mental status, neurological examination 6
• If no improvement or worsening, consider repeat lumbar puncture to assess CSF sterilization 6
• Ensure adequate antibiotic dosing for CSF penetration 7

Criteria for Treatment Success

• Patient becomes afebrile and clinically improving 3
• Resolution of altered mental status 8
• Improvement in meningeal signs (neck stiffness, photophobia) 9

Outpatient Antibiotic Therapy Consideration

After 5 days of inpatient therapy, consider transitioning to outpatient parenteral antibiotic therapy (OPAT) if 3, 1:

• Patient is afebrile and clinically improving
• Reliable intravenous access is established
• Patient can access 24-hour medical care from OPAT team
• No other acute medical needs exist

OPAT regimen:

• Ceftriaxone 2g IV once daily (after first 24 hours of twice-daily dosing) 3
• This provides cost savings and psychological benefits while maintaining therapeutic efficacy 3

Special Considerations and Pitfalls

Common Pitfalls to Avoid

• Never delay antibiotics for imaging or additional diagnostic procedures 1, 2
  • Treatment delay significantly increases mortality and neurological complications 1
• Do not underdose antibiotics 7
  • Meningitis requires high-dose bactericidal therapy to overcome the blood-brain barrier and achieve adequate CSF concentrations 7
• Do not omit dexamethasone 2
  • Must be given before or with first antibiotic dose to maximize benefit 2
• Do not stop antibiotics prematurely 3
  • Complete the full 10-14 day course even if clinical improvement occurs earlier 3, 6

Penicillin Allergy Considerations

• If true penicillin allergy exists, ceftriaxone or cefotaxime remain appropriate alternatives 5
• For severe beta-lactam allergy, consider fluoroquinolones (moxifloxacin) or vancomycin, though these are less well-studied for this indication 3, 5

Antibiotic Resistance Monitoring

• While Group C and G streptococci typically remain penicillin-susceptible, obtain susceptibility testing on the CSF isolate 5
• Adjust therapy if unexpected resistance patterns emerge 5

Supportive Care

Critical Care Considerations

• Transfer to ICU if 1:
  • Glasgow Coma Scale ≤12
  • Cardiovascular instability
  • Requiring specific organ support or intensive monitoring
• Maintain adequate fluid management and hemodynamic support 9
• Monitor for complications: seizures, increased intracranial pressure, cerebral edema 8