What is the recommended treatment for a Group B (Urethral Tract Infection) UTI in the third trimester of pregnancy?

Treatment of Group B Streptococcal UTI in Third Trimester of Pregnancy

For Group B Streptococcal (GBS) urinary tract infection in the third trimester of pregnancy, penicillin G (5 million units IV initial dose, then 2.5-3.0 million units IV every 4 hours until delivery) or ampicillin (2 g IV initial dose, then 1 g IV every 4 hours until delivery) is the recommended treatment.

Diagnosis and Significance

• GBS bacteriuria during pregnancy is a marker for heavy genital tract colonization and increases the risk of early-onset GBS disease in newborns 1
• Any colony count of GBS in urine during pregnancy is significant and should be treated, though most data on risk comes from studies with significant bacteriuria (>10^5 CFU/mL) 1, 2
• Women with GBS bacteriuria should not be re-screened in the third trimester as they are presumed to be GBS colonized 2

Treatment Recommendations

First-line Treatment Options:

• Intravenous therapy:
  • Penicillin G: 5 million units IV initial dose, then 2.5-3.0 million units IV every 4 hours until delivery 3
  • Ampicillin: 2 g IV initial dose, then 1 g IV every 4 hours until delivery 3

For Penicillin-Allergic Patients:

• Non-anaphylactic allergy:
  • Cefazolin: 2 g IV initial dose, then 1 g IV every 8 hours until delivery 3
• Anaphylactic allergy:
  • Clindamycin: 900 mg IV every 8 hours until delivery (if GBS isolate is susceptible) 3
  • Vancomycin: 1 g IV every 12 hours until delivery (if GBS isolate is resistant or susceptibility unknown) 3

Oral Treatment for Outpatient Management:

• For uncomplicated GBS UTI without systemic symptoms, oral therapy may be considered:
  • Erythromycin: 500 mg orally four times daily for at least 7 days 4
  • Alternative: Cephalexin (if not allergic to penicillin) 3

Duration of Treatment

• For symptomatic UTI: 7-10 days of appropriate antibiotics 3
• For asymptomatic bacteriuria: Treatment is still required, typically for 3-5 days depending on the antimicrobial used 1
• Regardless of previous treatment during pregnancy, intrapartum antibiotic prophylaxis is still required during labor 3, 2

Important Considerations

1. Antibiotic resistance: E. coli resistance patterns are important to consider, but GBS remains universally susceptible to penicillin 5

2. Recurrence risk: Antibiotics do not eliminate GBS from genitourinary and gastrointestinal tracts, and recolonization after treatment is typical 1

3. Intrapartum prophylaxis: Women with GBS bacteriuria at any point during pregnancy require intrapartum antibiotic prophylaxis during labor to prevent early-onset neonatal GBS disease 1, 3

4. Dosing interval: The dosing interval for penicillin G should be 4 hours to ensure anti-GBS activity in all patients 6

5. Monitoring: Follow-up urine culture after treatment completion is recommended to ensure cure

Pitfalls to Avoid

• Do not treat asymptomatic bacteriuria with oral antibiotics alone in the third trimester as this is ineffective for eliminating GBS colonization 3
• Do not assume that previous treatment for GBS UTI during pregnancy eliminates the need for intrapartum prophylaxis 1, 3
• Do not use trimethoprim-sulfamethoxazole in the third trimester due to risk of kernicterus 7
• Do not re-screen women with documented GBS bacteriuria by genital tract culture or urinary culture in the third trimester 2

By following these evidence-based recommendations, you can effectively treat GBS UTI in the third trimester while minimizing risks to both mother and baby.