Treatment for Group B Streptococcus (Strep B) Infections
Penicillin G is the treatment of choice for Group B streptococcal infections due to its proven efficacy, safety, narrow spectrum, and low cost. 1
First-Line Treatment Options
- Penicillin G is the first-line treatment for invasive Group B streptococcal (GBS) infections in adults, with a recommended dosage of 12-20 million units/day divided every 4-6 hours for 2-4 weeks, depending on the type of infection 1
- Ampicillin is an acceptable alternative to penicillin G, particularly in young children due to better taste acceptance 1
- For severe infections such as sepsis, penicillin or ampicillin should be combined with gentamicin for synergistic effect 1, 2
Treatment for Penicillin-Allergic Patients
- For patients with non-severe penicillin allergy (no history of anaphylaxis), first-generation cephalosporins like cefazolin are appropriate alternatives 3, 4
- For patients with severe penicillin allergy (high risk of anaphylaxis), clindamycin is recommended if the GBS isolate is susceptible to this antibiotic 1, 3
- If GBS isolate susceptibility is unknown or shows resistance to clindamycin, vancomycin should be used in penicillin-allergic patients 1, 3
- Important: Approximately 20% of GBS isolates are resistant to clindamycin, so susceptibility testing should always be performed before using this antibiotic 5
Treatment by Infection Type
Invasive GBS Infections in Adults
- For bacteremia and soft tissue infections: Penicillin G 12-20 million units/day IV divided every 4-6 hours 1, 6
- For endocarditis: Penicillin G for 4 weeks, often combined with gentamicin 1
- For osteomyelitis, pneumonia, and other serious infections: High-dose penicillin G with surgical management when appropriate (particularly for soft-tissue or bone infections) 6
Neonatal GBS Infections
- For suspected or confirmed neonatal sepsis: Combination of ampicillin (100-200 mg/kg/day divided in 4-6 doses) and gentamicin (3 mg/kg/day) 1
- For meningitis: Treatment duration of 14-21 days 1
- All newborns with signs of sepsis should undergo a full diagnostic evaluation (including lumbar puncture) and receive empirical antimicrobial therapy immediately 5
Intrapartum Antibiotic Prophylaxis (IAP)
- For GBS-positive pregnant women: Penicillin G IV with initial dose of 5 million units, followed by 2.5-3 million units every 4 hours until delivery 1, 3
- Alternative for IAP: Ampicillin 2g IV initial dose, followed by 1g every 4 hours until delivery 1
- For penicillin-allergic pregnant women not at high risk for anaphylaxis: Cefazolin 2g IV initial dose, then 1g IV every 8 hours until delivery 3
- Adequate IAP is defined as ≥4 hours of penicillin, ampicillin, or cefazolin before delivery 5, 3
Duration of Treatment
- For invasive infections: 2-4 weeks depending on infection site and severity 1
- For endocarditis: 4 weeks of therapy 1
- For meningitis: 14-21 days 1
- For intrapartum prophylaxis: Continue until delivery 3
Important Clinical Considerations
- Intramuscular benzathine penicillin G (Bicillin L-A) alone is insufficient for eradicating GBS colonization in pregnant women but may be useful as adjunctive treatment for patients at risk for rapid delivery 7
- The incidence of resistance to non-beta-lactam antibiotics (clindamycin, erythromycin, and fluoroquinolones) has increased, making susceptibility testing crucial 8
- Penicillin G remains effective against GBS, with only rare isolates showing reduced susceptibility 8
By following these evidence-based treatment recommendations, clinicians can effectively manage Group B streptococcal infections while minimizing morbidity and mortality in affected patients.