What is the recommended treatment for non-pregnant adults with Group B streptococcus (GBS) infection?

Treatment of Group B Streptococcus (GBS) Infection in Non-Pregnant Adults

For non-pregnant adults with Group B streptococcal (GBS) infection, penicillin G is the first-line treatment due to its narrow spectrum of activity and continued effectiveness against GBS. 1, 2

First-Line Treatment Options

• Penicillin G is the preferred agent for treating GBS infections in non-pregnant adults, typically administered at 5 million units IV initially, followed by 2.5-3.0 million units IV every 4 hours 1, 2
• Ampicillin is an acceptable alternative at 2g IV initial dose, followed by 1g IV every 4 hours 1
• GBS remains universally susceptible to beta-lactam antibiotics, though there have been isolated reports of reduced susceptibility in some countries 3

Treatment for Penicillin-Allergic Patients

• For patients with non-severe penicillin allergy (no history of anaphylaxis, angioedema, respiratory distress, or urticaria), cefazolin is recommended at 2g IV initial dose, followed by 1g IV every 8 hours 4
• For patients with severe penicillin allergy at high risk for anaphylaxis: 4
  • Clindamycin 900mg IV every 8 hours (if isolate is susceptible)
  • Vancomycin 1g IV every 12 hours (if susceptibility testing is not available or isolate is resistant to clindamycin)

Susceptibility Testing Considerations

• Susceptibility testing should be performed on GBS isolates from penicillin-allergic patients at high risk for anaphylaxis 4
• Resistance to second-line antibiotics such as erythromycin and clindamycin has been increasing in recent years 3, 1
• Erythromycin resistance increased from 8% to 18% between 1992 and 1994 in one study, suggesting macrolides should not be used empirically for treatment of patients with penicillin allergies 1

Special Treatment Considerations

• For severe invasive GBS infections, combination therapy with penicillin or ampicillin plus gentamicin may be considered as killing kinetics are accelerated by this combination 5
• For specific clinical syndromes:
  • Primary bacteremia (most common presentation in non-pregnant adults) 1, 2
  • Skin and soft tissue infections (second most common presentation) 1, 2
  • Urinary tract infections 1
  • Pneumonia 1
  • Peritonitis 1
  • Endocarditis (rare) 1

Risk Factors and Prognosis

• GBS bacteremia in non-pregnant adults is associated with underlying conditions including: 1, 2
  • Liver disease (35.3%)
  • Malignancies (33.3%)
  • Diabetes mellitus (27.5-42.6%)
• Poor prognostic factors include central nervous system diseases, alcoholism, shock, renal failure, and altered consciousness 1
• Independent risk factors for mortality include polymicrobial bacteremia, thrombocytopenia, and shock 2
• Overall mortality rate ranges from 20.2% to 33.3% 1, 2

Treatment Duration

• Treatment duration should be tailored to the site and severity of infection:
  • Uncomplicated bacteremia: 10-14 days 2
  • Soft tissue infections: 10-14 days 1
  • Endocarditis: 4-6 weeks 1
  • Meningitis: at least 14 days 2

Monitoring

• Blood cultures should be repeated to ensure clearance of bacteremia 2
• Clinical response should be monitored closely, particularly in patients with risk factors for poor outcomes 1
• Source control (drainage of abscesses, removal of infected catheters) is essential when applicable 1, 2

GBS infections in non-pregnant adults are increasing in incidence and carry significant morbidity and mortality, particularly in elderly patients with underlying conditions 1, 2. Prompt recognition and appropriate antibiotic therapy are essential for optimal outcomes.