What is the recommended treatment for a pregnant woman diagnosed with a Group B strep (Streptococcus agalactiae) urinary tract infection (UTI)?

Management of Group B Strep UTI in Pregnancy

For pregnant women with Group B streptococcal urinary tract infection, immediate treatment with intravenous penicillin G (5 million units IV initial dose, then 2.5 million units IV every 4 hours) or ampicillin (2 g IV initial dose, then 1 g IV every 4 hours) is recommended, followed by intrapartum prophylaxis during labor regardless of previous treatment. 1

Diagnosis and Assessment

• GBS UTI is diagnosed when urine culture shows ≥50,000 CFUs/mL of GBS with symptoms of UTI 1
• Any amount of GBS in urine during pregnancy indicates heavy colonization and requires both immediate treatment and intrapartum prophylaxis during labor 1

Treatment Algorithm

First-Line Treatment (Non-Penicillin Allergic Patients):

1. Penicillin G: 5 million units IV initial dose, then 2.5 million units IV every 4 hours until delivery 2, 1

   • Preferred due to narrow spectrum of activity and lower likelihood of selecting for resistant organisms

2. Alternative: Ampicillin 2 g IV initial dose, then 1 g IV every 4 hours until delivery 2, 1

For Penicillin-Allergic Patients:

• For patients not at high risk for anaphylaxis:

  • Cefazolin: 2 g IV initial dose, then 1 g IV every 8 hours until delivery 2, 1

• For patients at high risk for anaphylaxis (history of immediate hypersensitivity reactions):

  • If susceptibility testing available and isolate is susceptible:

    • Clindamycin: 900 mg IV every 8 hours until delivery 2, 1
    • OR Erythromycin: 500 mg IV every 6 hours until delivery 2

  • If susceptibility unknown, testing not possible, or resistance to clindamycin/erythromycin:

    • Vancomycin: 1 g IV every 12 hours until delivery 2, 1

Important Considerations

Antibiotic Resistance Patterns

• 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, 3

Treatment Duration

• Treatment should be continued for 7-10 days for uncomplicated UTIs and 10-14 days for complicated UTIs or pyelonephritis 1
• Treatment should continue for at least 48-72 hours after symptoms resolve 1

Follow-up

• Obtain follow-up urine culture after completion of treatment to confirm eradication 1
• Screening for GBS at 35-37 weeks gestation is still recommended, regardless of previous GBS UTI treatment 1

Intrapartum Prophylaxis

• All women with GBS bacteriuria during pregnancy should receive intrapartum antibiotic prophylaxis during labor, regardless of whether they received treatment earlier in pregnancy 1
• The recommended prophylaxis regimen during labor is the same as the treatment regimen:
  • 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

Pitfalls to Avoid

1. Do not use oral antimicrobial agents alone to treat women who are found to be colonized with GBS during prenatal screening. Such treatment is not effective in eliminating carriage or preventing neonatal disease 2

2. Do not skip intrapartum prophylaxis even if the patient was previously treated for GBS UTI during pregnancy 1

3. Avoid trimethoprim-sulfamethoxazole (TMP-SMX) as empiric therapy for GBS UTIs, as Group B streptococci are frequently resistant 1

4. Avoid tetracyclines including doxycycline in pregnancy due to potential harmful effects 1

5. Do not use erythromycin if other options are available due to increasing resistance 1

6. Do not use fluoroquinolones for uncomplicated UTIs when alternatives exist, due to FDA warnings about serious side effects 1