What are the potential sources of infection and treatment for Group B Streptococcus (GBS) bacteremia?

Potential Sources of Group B Streptococcus (GBS) Bacteremia

Group B Streptococcus bacteremia most commonly originates from the urinary tract, skin/soft tissue infections, pneumonia, or can present as primary bacteremia, particularly in patients with underlying conditions such as diabetes mellitus. 1, 2

Common Sources of GBS Bacteremia in Adults

Primary Sites of Infection

• Skin and soft tissue infections are the most common source of GBS bacteremia in adults, particularly in women 3
• Urinary tract infections are a significant source, especially in men and those with urinary tract abnormalities 3, 4
• Pneumonia is a common clinical syndrome in adults with GBS bacteremia (46.5% in some studies) 2
• Primary bacteremia with no identifiable source accounts for approximately 50% of GBS bacteremia cases 3

Less Common Sources

• Bone and joint infections including septic arthritis (more common in women) 2, 3
• Peritonitis (23.1% in some studies) 2
• Meningitis (8% in some studies) 2
• Intravascular device infections (7.7% in some studies) 2

Risk Factors for GBS Bacteremia in Adults

• Age ≥60 years (62.2% of cases occur in this age group) 3
• Diabetes mellitus (most significant underlying disease in many studies) 1, 2
• Cardiovascular diseases (present in 53.8% of cases in some studies) 2
• Urinary tract abnormalities (present in 60% of cases with urinary source) 4
• Chronic renal failure (27% of cases with urinary source) 4
• Liver disease/alcohol abuse (more common in males) 2, 3
• Malignancy (more common in females) 2, 3
• Immunocompromised states including HIV infection 1, 2

Diagnostic Considerations

• Blood cultures are essential for diagnosis 2
• When GBS bacteremia is identified, consider the following evaluations:
  • Skin examination for cellulitis or soft tissue infections 1, 3
  • Urinalysis and urine culture to identify urinary source 4
  • Chest imaging if respiratory symptoms are present 2
  • Joint aspiration if arthritis is suspected 2, 3

Treatment Approach

• First-line therapy for GBS bacteremia is intravenous penicillin G or ampicillin 5, 6

  • For adults with GBS septicemia: Penicillin G 12-20 million units/day divided every 4-6 hours 6
  • Alternative: Ampicillin 2 grams IV every 4-6 hours 5

• Duration of therapy depends on the source:

  • Uncomplicated bacteremia: 10-14 days of therapy 7
  • With identified focus (endocarditis, osteomyelitis): 4-6 weeks 6
  • Consider source control (drainage, debridement) when appropriate 6

Special Considerations

• GBS in urine in non-pregnant adults should only be treated if symptomatic or in patients with underlying urinary tract abnormalities 8
• Polymicrobial bacteremia is common (45.4% in some studies), with Staphylococcus aureus being the most common concurrent isolate 2
• Mortality rates range from 15-32% in adults with GBS bacteremia, with an attributable mortality of approximately 7.8% 2, 3

Prevention Strategies

• Optimal management of underlying conditions, particularly diabetes mellitus 1
• Proper skin care, especially in patients with diabetes or peripheral vascular disease 3
• Consider screening for urinary tract abnormalities in patients with GBS urinary tract infections 4