What is the recommended treatment for a Group B streptococcal (GBS) urinary tract infection (UTI)?

Treatment of Group B Streptococcal (GBS) Urinary Tract Infections

Penicillin G or ampicillin are the first-line treatments for Group B streptococcal urinary tract infections due to their narrow spectrum of activity and lower likelihood of selecting for resistant organisms. 1

First-Line Treatment Options

For non-pregnant adults with GBS UTI:

• Penicillin G: 5 million units IV initially, then 2.5 million units IV every 4 hours (for severe infections)
• Ampicillin: 2 g IV initially, then 1 g IV every 4-6 hours (for severe infections)
• Cephalexin: 500 mg orally four times daily (for uncomplicated infections) 1
• Nitrofurantoin: Can be effective for uncomplicated lower UTIs caused by GBS 1

Alternative Treatments (Penicillin Allergy)

For patients with penicillin allergy:

• Cefazolin: 2 g IV initial dose, then 1 g IV every 8 hours (if no history of anaphylaxis) 1
• Clindamycin: 900 mg IV every 8 hours (only if susceptibility testing confirms sensitivity) 1
• Vancomycin: 1 g IV every 12 hours (for clindamycin-resistant strains) 1

Treatment Duration

• Uncomplicated UTIs: 7-10 days
• Complicated UTIs or pyelonephritis: 10-14 days
• Continue treatment for at least 48-72 hours after symptoms resolve 1

Antibiotic Resistance Considerations

GBS resistance patterns are important to consider when selecting treatment:

• All GBS isolates generally remain susceptible to penicillin, ampicillin, cefazolin, and vancomycin 1
• Resistance rates to alternative agents include:
  • 21% resistance to erythromycin
  • 4% resistance to clindamycin
  • 81.6% resistance to tetracycline
  • 68.9% resistance to co-trimoxazole 1

Recent research from Iran (2023) showed concerning resistance patterns with 18.3% resistance to penicillin and 81.6% to ampicillin, highlighting the importance of local resistance patterns 2. However, this is not consistent with most global data and may represent regional variation.

Special Considerations for Pregnant Women

GBS UTIs in pregnancy require special attention:

• Any amount of GBS in urine during pregnancy indicates heavy colonization 1
• Treatment of current infection is required, followed by intrapartum prophylaxis during labor 1
• Screening for GBS at 35-37 weeks gestation is recommended regardless of previous GBS UTI treatment 1, 3
• Follow-up urine culture after completion of treatment is recommended to confirm eradication 1

Intrapartum Prophylaxis During Labor

For women with history of GBS bacteriuria during pregnancy:

• Penicillin G: 5 million units IV initially, then 2.5 million units IV every 4 hours until delivery, or
• Ampicillin: 2 g IV initially, then 1 g IV every 4 hours until delivery 1

Clinical Pitfalls to Avoid

1. Avoid trimethoprim-sulfamethoxazole (TMP-SMX) as empiric therapy for GBS UTIs due to frequent resistance 1
2. Avoid erythromycin and macrolides when possible due to increasing resistance 1
3. Avoid tetracyclines in pregnancy and children under 8 years due to potential harmful effects 1
4. Avoid fluoroquinolones for uncomplicated UTIs when alternatives exist due to FDA warnings about serious side effects 1
5. Do not re-screen women with documented GBS bacteriuria by genital tract culture or urinary culture in the third trimester, as they are presumed to be GBS colonized 4
6. Do not treat asymptomatic women with urinary GBS colony counts <100,000 CFU/mL with antibiotics for prevention of adverse outcomes such as pyelonephritis, chorioamnionitis, or preterm birth 4

Risk Assessment

GBS UTIs appear to have a lower risk of progression to pyelonephritis compared to E. coli UTIs. Recent research (2024) shows that E. coli UTIs progress to pyelonephritis at markedly higher rates (15.6%) than GBS UTIs (1.1%) 5. However, this should not affect the decision to treat symptomatic GBS UTIs appropriately.