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

Treatment of Group B Streptococcus Urinary Tract Infection

Penicillin G or ampicillin is the first-line treatment for Group B Streptococcus (GBS) urinary tract infections due to their narrower spectrum of activity and lower likelihood of selecting for resistant organisms. 1

First-Line Treatment Options

• Ampicillin: 500 mg orally four times daily for uncomplicated UTIs 1, 2

  • For severe infections, higher doses may be required
  • Treatment should continue for 7-10 days for uncomplicated UTIs and 10-14 days for complicated UTIs 1
  • Should be administered at least 30 minutes before or 2 hours after meals for maximal absorption 2

• Penicillin G: Recommended as first-line therapy along with ampicillin 1

  • Treatment should continue for at least 48-72 hours after the patient becomes asymptomatic 3
  • For streptococcal infections, a minimum of 10 days' treatment is recommended to prevent complications like rheumatic fever or glomerulonephritis 3

Alternative Treatment Options for Penicillin-Allergic Patients

For patients with penicillin allergy, the following alternatives can be considered:

• Cefazolin: 2 g IV initial dose, then 1 g IV every 8 hours 1
• Cephalexin: Oral option for outpatient treatment 1
• Clindamycin: 900 mg IV every 8 hours, but only if susceptibility testing confirms sensitivity 1
• Vancomycin: 1 g IV every 12 hours (for clindamycin-resistant strains) 1
• Nitrofurantoin: May be effective for uncomplicated lower UTIs caused by GBS 1, 4

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

Medications to Avoid

• Trimethoprim-sulfamethoxazole (TMP-SMX): Not recommended as empiric therapy due to frequent resistance 1
• Erythromycin: Not recommended due to increasing resistance 1
• Tetracyclines: Contraindicated in pregnancy and children under 8 years 1
• Fluoroquinolones: Should be avoided when alternatives exist due to FDA warnings about serious side effects 1

Special Considerations for Pregnant Women

• Any amount of GBS in urine during pregnancy indicates heavy colonization and requires both immediate treatment and intrapartum prophylaxis during labor 1
• Screening for GBS at 35-37 weeks gestation is recommended regardless of previous GBS UTI treatment 1
• Follow-up urine culture after treatment completion is necessary to confirm eradication 1
• Intrapartum prophylaxis recommendations:
  • Penicillin G: 5 million units IV initially, then 2.5 million units IV every 4 hours until delivery
  • Ampicillin: 2 g IV initially, then 1 g IV every 4 hours until delivery 1

Diagnosis Confirmation

• A positive urine culture with ≥50,000 CFUs/mL of GBS with symptoms of UTI confirms the diagnosis 1
• For pregnant women, any amount of GBS in urine requires treatment 1

Treatment Duration

• For uncomplicated UTIs: 7-10 days
• For complicated UTIs or pyelonephritis: 10-14 days
• Treatment should continue for at least 48-72 hours after symptoms resolve 1
• For streptococcal infections, a minimum of 10 days' treatment is recommended 3

Common Pitfalls to Avoid

1. Failing to obtain susceptibility testing for penicillin-allergic patients
2. Using trimethoprim-sulfamethoxazole empirically despite high resistance rates
3. Not treating GBS bacteriuria in pregnant women regardless of colony count
4. Inadequate treatment duration (less than 7 days for uncomplicated UTIs)
5. Not following up with urine cultures after treatment in pregnant women