What is the recommended treatment for Streptococcus pneumoniae (Strep pneumonia) infection?

Treatment of Streptococcus pneumoniae Infection

For Streptococcus pneumoniae infections, penicillin G or amoxicillin remains the first-line treatment for penicillin-susceptible strains, while ceftriaxone or cefotaxime is recommended for penicillin-resistant strains. The choice of antibiotic depends on the severity of infection, local resistance patterns, and patient factors.

Treatment Algorithm Based on Penicillin Susceptibility

Penicillin-Susceptible S. pneumoniae (MIC <2 μg/mL)

• First-line options:

  • Parenteral therapy: Penicillin G (200,000-250,000 U/kg/day every 4-6 hours) or Ampicillin (150-200 mg/kg/day every 6 hours) 1
  • Oral therapy: Amoxicillin (90 mg/kg/day in 2 doses or 1 g PO q8h for adults) 1

• Alternative options:

  • Ceftriaxone (50-100 mg/kg/day every 12-24 hours or 1-2 g IV q12h for adults)
  • Cefotaxime (150 mg/kg/day every 8 hours or 1-2 g IV q8h for adults)
  • Respiratory fluoroquinolones (Levofloxacin 750 mg IV/PO daily or Moxifloxacin 400 mg IV/PO daily) 2, 3, 4

Penicillin-Resistant S. pneumoniae (MIC ≥4 μg/mL)

• First-line options:

  • Parenteral therapy: Ceftriaxone (100 mg/kg/day every 12-24 hours or 1-2 g IV q12h for adults) 1

• Alternative options:

  • High-dose Ampicillin (300-400 mg/kg/day every 6 hours)
  • Levofloxacin (750 mg IV/PO daily) 3
  • Moxifloxacin (400 mg IV/PO daily) 4
  • Vancomycin (40-60 mg/kg/day every 6-8 hours) for highly resistant strains 1
  • Linezolid (30 mg/kg/day every 8 hours for children <12 years; 600 mg PO/IV q12h for adults) 1

Treatment Based on Clinical Presentation

Community-Acquired Pneumonia (CAP)

• Outpatient (previously healthy):

  • Amoxicillin (1 g PO q8h) 1
  • Alternative: Doxycycline or a macrolide (if local resistance is <25%) 1, 2

• Outpatient (with comorbidities or risk factors for DRSP):

  • Respiratory fluoroquinolone (Moxifloxacin 400 mg PO daily or Levofloxacin 750 mg PO daily) 1, 2
  • Alternative: β-lactam plus a macrolide 1

• Inpatient (non-ICU):

  • β-lactam (Ceftriaxone, Cefotaxime, or Ampicillin) plus a macrolide 1
  • Alternative: Respiratory fluoroquinolone monotherapy 1, 2

• Inpatient (ICU):

  • β-lactam (Ceftriaxone, Cefotaxime, or Ampicillin-sulbactam) plus either Azithromycin or a respiratory fluoroquinolone 1

Meningitis

• First-line: Ceftriaxone or Cefotaxime (high-dose) 5
• Add Vancomycin if high-level penicillin resistance is suspected until susceptibility results are available 5

Duration of Therapy

• Standard CAP treatment: 7-10 days 2
• Uncomplicated infections: 5-7 days 2
• Severe infections: 10-14 days 2

Switching to Oral Therapy

Switch to oral therapy when the patient is:

• Afebrile for 24 hours
• Showing clinical improvement
• Able to tolerate oral medications 2

Important Clinical Considerations

Penicillin Resistance

• Despite increasing penicillin resistance, high-dose penicillin therapy remains effective for non-meningeal pneumococcal infections because achievable serum and pulmonary levels exceed the MICs of most strains 6, 7
• For pneumococcal pneumonia, treatment failure with appropriate β-lactam therapy is rare, even with penicillin-intermediate strains 5

Monitoring Response

• Assess clinical response within 48-72 hours of initiating therapy
• Consider treatment failure if no improvement is observed within 72 hours 2
• Follow-up evaluation at approximately 6 weeks after treatment is recommended 2

Common Pitfalls to Avoid

1. Overuse of broad-spectrum antibiotics: Reserve carbapenems and vancomycin for highly resistant strains or treatment failures 2, 8
2. Inadequate dosing: Ensure high-dose therapy for suspected resistant strains 5
3. Ignoring local resistance patterns: Treatment should be guided by local epidemiology of resistance 1, 2
4. Premature antibiotic discontinuation: Complete the full course of antibiotics to prevent relapse and resistance development 2

By following this treatment algorithm and considering the patient's clinical presentation, severity of illness, and local resistance patterns, optimal outcomes can be achieved in the management of Streptococcus pneumoniae infections.