What is the recommended treatment for a non-pregnant patient with a group B strep (Streptococcus agalactiae) infection?

Treatment of Group B Streptococcus in Non-Pregnant Adults

For non-pregnant adults with invasive Group B Streptococcus infections, high-dose intravenous penicillin G is the treatment of choice, with a recommended dosage of 12-20 million units per day divided every 4-6 hours, with treatment duration ranging from 2-6 weeks depending on the infection site. 1, 2

First-Line Antibiotic Therapy

• Penicillin G is the preferred agent because GBS has minimum inhibitory concentrations that are 4-8 fold higher than Group A streptococci, necessitating higher doses than typical streptococcal infections 3
• The standard dosing is 12-20 million units per day administered intravenously in divided doses every 4-6 hours 1, 2
• Ampicillin is an acceptable alternative to penicillin G, though penicillin G remains preferred due to its narrower spectrum and reduced risk of selecting resistant organisms 4

Duration of Treatment by Infection Type

• Bacteremia without identified source: 2 weeks of IV therapy 1
• Endocarditis: 4-6 weeks of continuous IV therapy 1, 2
• Meningitis: 2-3 weeks of IV therapy 1
• Osteomyelitis and soft tissue infections: 4-6 weeks, often requiring surgical debridement in addition to antibiotics 1, 2
• Pneumonia and urosepsis: Minimum 2 weeks, extended based on clinical response 2, 3

Penicillin-Allergic Patients

• For patients with non-severe penicillin allergy (no history of anaphylaxis, angioedema, or respiratory distress), cefazolin 2g IV initially, then 1g IV every 8 hours is the preferred alternative 5
• For patients at high risk for anaphylaxis, clindamycin 900 mg IV every 8 hours or vancomycin 1g IV every 12 hours should be used 5
• Critical pitfall: Approximately 20% of GBS isolates are resistant to clindamycin, so susceptibility testing must be performed before using this agent 6, 7
• Erythromycin resistance is increasing and often correlates with clindamycin resistance, making susceptibility testing mandatory 3, 4

Special Considerations for High-Risk Populations

• Elderly patients and those with diabetes, malignancy, liver disease, or neurological impairment have significantly higher mortality rates from invasive GBS disease 2, 3
• Nosocomial infections are common, particularly related to IV catheter placement 3
• Recurrent infection occurs in 4.3% of survivors, warranting close follow-up 3
• Polymicrobial bacteremia occurs frequently; if suspected, broader spectrum coverage may be needed initially until cultures clarify the microbiology 2

Surgical Management

• Surgical debridement is often required for successful treatment of soft tissue infections, osteomyelitis, and infectious arthritis in addition to antibiotic therapy 1, 2
• Early identification and aggressive treatment, including surgical intervention when indicated, improves outcomes in elderly and immunocompromised patients 2

Critical Clinical Pitfalls to Avoid

• Do not use oral antibiotics for invasive GBS disease—IV therapy is required for serious infections 1, 2
• Do not underdose penicillin—GBS requires higher doses than other streptococcal species due to higher MICs 3
• Do not use clindamycin without susceptibility testing due to the 20% resistance rate 6, 7
• Do not stop antibiotics prematurely—complete the full course based on infection type to prevent recurrence 2