What oral antibiotics are recommended for treating Group B strep (Streptococcus agalactiae) urinary tract infections (UTIs) in pregnancy?

Treatment of Group B Streptococcus UTI in Pregnancy

For Group B streptococcus (GBS) urinary tract infections during pregnancy, 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 first-line treatments, with oral amoxicillin as an appropriate outpatient option. 1

First-Line Treatment Options

Intravenous Options

• Penicillin G: 5 million units IV initial dose, then 2.5-3.0 million units IV every 4 hours
• Ampicillin: 2 g IV initial dose, then 1 g IV every 4 hours

Oral Options (for outpatient management)

• Amoxicillin: Standard UTI dosing (typically 500 mg three times daily for 5-7 days)

Treatment Algorithm for Penicillin-Allergic Patients

For patients with non-severe penicillin allergy:

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

For patients with severe penicillin allergy (history of anaphylaxis, angioedema, respiratory distress, or urticaria):

1. If susceptibility testing available and isolate is susceptible to both clindamycin and erythromycin:

   • Clindamycin: 900 mg IV every 8 hours 2, 1

2. If isolate is resistant to erythromycin but susceptible to clindamycin:

   • Use clindamycin only if testing for inducible clindamycin resistance is negative 2, 1

3. If susceptibility testing unavailable OR isolate resistant to clindamycin OR inducible resistance present:

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

Important Clinical Considerations

Antimicrobial Resistance

• GBS remains universally susceptible to penicillin, making it the preferred treatment option 1
• Resistance to clindamycin (5-21%) and erythromycin (9-29%) has been documented and is increasing 3, 4, 5
• Susceptibility testing is essential when using alternatives to penicillin 1

Duration of Treatment

• For uncomplicated UTIs: 5-7 days 1
• For complicated UTIs or pyelonephritis: 10-14 days 1
• Continue treatment for at least 48-72 hours after symptoms resolve 1

Follow-Up and Intrapartum Prophylaxis

• Any colony count of GBS in urine during pregnancy is considered significant and indicates heavy genital tract colonization 1
• All pregnant women with GBS bacteriuria at any point during pregnancy require intrapartum antibiotic prophylaxis during labor, regardless of previous treatment 1
• Antibiotics do not eliminate GBS from genitourinary and gastrointestinal tracts, and recolonization after treatment is typical 1

Common Pitfalls to Avoid

1. Inadequate susceptibility testing: Always perform susceptibility testing for penicillin-allergic patients due to increasing resistance to alternative antibiotics 1

2. Treating with oral antibiotics alone in severe cases: IV antibiotics may be necessary for pyelonephritis or severe UTI symptoms 1

3. Failure to provide intrapartum prophylaxis: Even if GBS UTI was treated earlier in pregnancy, intrapartum prophylaxis is still required during labor 2, 1

4. Using erythromycin: Erythromycin is no longer recommended for GBS prophylaxis due to increasing resistance and poor placental transfer 2, 1

5. Attempting to eradicate colonization: Treating GBS colonization with oral antibiotics in the third trimester is ineffective, as 30-70% of treated women remain colonized at delivery 1

By following these evidence-based recommendations, clinicians can effectively treat GBS UTI in pregnancy while minimizing risks to both mother and baby.