Treatment of Streptococcus Pneumoniae Infections
Amoxicillin is the first-line treatment for Streptococcus pneumoniae infections, with dosing of 1g three times daily for adults and 80-100 mg/kg/day in three doses for children. 1
First-Line Therapy Options
For Non-Severe Community-Acquired Pneumonia:
- Adults: Amoxicillin 1g three times daily (3g/day) 2, 1
- Children: Amoxicillin 90 mg/kg/day in 2 doses or 45 mg/kg/day in 3 doses 2
For Hospitalized Patients:
- Fully immunized children without high-level penicillin resistance: Ampicillin (150-200 mg/kg/day every 6 hours) or penicillin G (200,000-250,000 U/kg/day every 4-6 hours) 2
- Adults requiring hospitalization: Ceftriaxone, cefotaxime, or high-dose ampicillin 1
Treatment Based on Penicillin Susceptibility
S. pneumoniae with MICs for penicillin <2.0 µg/mL:
- Parenteral therapy: Ampicillin or penicillin G; alternatives include ceftriaxone or cefotaxime 2
- Oral step-down: Amoxicillin 2
S. pneumoniae resistant to penicillin (MICs ≥4.0 µg/mL):
- Parenteral therapy: Ceftriaxone (100 mg/kg/day); alternatives include high-dose ampicillin, levofloxacin, or linezolid 2
- Oral therapy: Levofloxacin or linezolid (if susceptible) 2
Special Considerations
For Patients with Penicillin Allergy:
- Respiratory fluoroquinolones (e.g., levofloxacin)
- Macrolides (with caution due to increasing resistance)
- Linezolid (for resistant strains) 1, 3
Important Cautions:
- Trimethoprim-sulfamethoxazole is not recommended due to inadequate activity against S. pneumoniae 2, 1
- First-generation cephalosporins are not recommended due to inadequate activity 2
- Macrolides alone are not recommended for empiric therapy in areas with high pneumococcal resistance 1
Duration of Therapy
- Standard duration for uncomplicated pneumococcal pneumonia: 5-7 days 1, 4
- For bacteremia: Short-course therapy (5-10 days) may be appropriate for clinically stable patients with pneumonia as the source 5
- Assess clinical response within 48-72 hours of initiating therapy 1
Clinical Pearls
- High-dose penicillin G therapy (continuous infusion of 20-24 million units per day) can achieve serum levels that exceed MICs of most PRSP strains 6
- Despite concerns about penicillin resistance, standard doses of beta-lactams remain effective for most pneumococcal pneumonia cases as the achievable lung concentrations exceed the MICs 7
- For severe infections or in regions with high-level penicillin resistance, third-generation cephalosporins (ceftriaxone, cefotaxime) are recommended 2, 1
Monitoring and Follow-up
- Clinical response should be assessed within 48-72 hours of initiating therapy
- Consider chest radiograph at 6 weeks for patients with persistent symptoms 1
- If no improvement within 72 hours, reevaluate diagnosis and consider alternative pathogens or resistance 2, 1
Remember that local resistance patterns should guide empiric therapy choices, and treatment should be adjusted based on culture and susceptibility results when available.