What is the recommended treatment for Group B strep (Streptococcus agalactiae) urinary tract infection?

Treatment of Group B Streptococcal Urinary Tract Infection

For Group B streptococcal (GBS) urinary tract infections, penicillin G (5 million units IV initial dose, then 2.5-3.0 million units IV every 4 hours) or ampicillin (2 g IV initial dose, then 1 g IV every 4 hours) are the recommended first-line treatments due to their narrow spectrum of activity and proven effectiveness against GBS. 1

First-Line Treatment Options

For Non-Pregnant Adults:

• Penicillin G: 5 million units IV initial dose, then 2.5 million units IV every 4 hours 1
• Ampicillin: 2 g IV initial dose, then 1 g IV every 4 hours 1
• Oral Ampicillin: 500 mg four times daily for uncomplicated UTIs 2

For Penicillin-Allergic Patients:

Based on allergy severity and susceptibility testing:

• Low risk of anaphylaxis: Cefazolin 2 g IV initial dose, then 1 g IV every 8 hours 1
• High risk of anaphylaxis:
  • If GBS is susceptible: Clindamycin 900 mg IV every 8 hours 1
  • If GBS is resistant or susceptibility unknown: Vancomycin 1 g IV every 12 hours 1

Special Considerations for Pregnant Women

GBS bacteriuria during pregnancy requires special attention as it:

1. Indicates heavy colonization
2. Increases risk of preterm delivery
3. Necessitates intrapartum antibiotic prophylaxis during delivery 1

Treatment recommendations:

• Same antibiotics as non-pregnant adults (penicillin G or ampicillin preferred)
• Follow-up urine culture after completion of treatment to confirm eradication 1
• GBS screening at 35-37 weeks gestation regardless of previous GBS UTI treatment 3

Treatment Duration

• For uncomplicated UTIs: 7-10 days of therapy
• For complicated UTIs or pyelonephritis: 10-14 days of therapy
• Treatment should continue for at least 48-72 hours after the patient becomes asymptomatic 2

Important Clinical Pearls

1. Susceptibility testing: Due to increasing resistance, susceptibility testing should be performed for penicillin-allergic patients 1

2. Avoid macrolides when possible: Erythromycin is not recommended due to increasing resistance among GBS isolates 3

3. Pregnancy impact: A double-blind controlled study showed that treating GBS in urine during pregnancy significantly reduced rates of premature rupture of membranes (11% vs 53%) and preterm labor (5.4% vs 38%) 4

4. Asymptomatic colonization: Outside of pregnancy, asymptomatic GBS colonization should not be treated except in cases of UTI 1

5. Monitoring: For chronic urinary infections, frequent bacteriologic and clinical assessment is necessary during therapy and may be required for several months afterward 2

By following these evidence-based recommendations, clinicians can effectively treat GBS urinary tract infections while minimizing complications and reducing the risk of antimicrobial resistance.