What is the recommended treatment for a patient with an isolated Group B strep (GBS) urine culture with mixed urogenital flora?

Treatment of Isolated Group B Strep in Urine with Mixed Urogenital Flora

Women with Group B Streptococcus (GBS) isolated from urine in any concentration during pregnancy should receive appropriate treatment for urinary tract infection followed by intrapartum antibiotic prophylaxis during labor, regardless of subsequent screening results. 1

Diagnosis and Management During Pregnancy

• GBS bacteriuria during pregnancy is a marker for heavy genital tract colonization and increases the risk for early-onset neonatal GBS disease, requiring both immediate treatment and later intrapartum prophylaxis 1, 2
• Laboratories should report GBS in urine culture specimens when present at concentrations of ≥10^4 colony-forming units/ml in pure culture or mixed with other microorganisms 1
• When GBS is found in urine with mixed urogenital flora, this still represents significant colonization requiring treatment 1

Initial Treatment Approach

• For symptomatic or asymptomatic GBS urinary tract infection detected during pregnancy, treat according to standard UTI protocols 1
• Treatment options include:
  • Amoxicillin 500 mg three times daily for 3-7 days
  • Nitrofurantoin 100 mg twice daily for 5-7 days (avoid in late pregnancy)
  • Cephalexin 500 mg four times daily for 3-7 days 1
• Important: Antibiotics given before the intrapartum period do not eliminate GBS from the genitourinary tract, and recolonization after treatment is typical 3, 1

Intrapartum Management

• All women with GBS bacteriuria during pregnancy require intrapartum antibiotic prophylaxis regardless of the concentration of bacteria found in the urine 1, 2
• No additional GBS screening at 35-37 weeks is needed for women with documented GBS bacteriuria during the current pregnancy 2

Recommended Intrapartum Antibiotic Regimens:

• For patients without penicillin allergy:

  • First choice: Penicillin G, 5 million units IV initial dose, then 2.5 million units IV every 4 hours until delivery 1, 2
  • Alternative: Ampicillin, 2 g IV initial dose, then 1 g IV every 4 hours until delivery 1, 2

• For patients with penicillin allergy:

  • Non-severe allergy (no anaphylaxis history): Cefazolin, 2 g IV initial dose, then 1 g IV every 8 hours until delivery 1
  • Severe allergy (high risk for anaphylaxis): Susceptibility testing for clindamycin should be performed 1
    • If susceptible: Clindamycin, 900 mg IV every 8 hours until delivery 1
    • If resistant or unknown: Consult infectious disease specialist 1

Special Considerations

• Women with planned cesarean delivery before labor onset and before membrane rupture do not require GBS prophylaxis, even with positive GBS urine culture 1
• For non-pregnant patients, GBS in urine with mixed flora should only be treated if the patient is symptomatic or has underlying urinary tract abnormalities 4
• Antibiotic resistance in GBS is increasing, particularly to second-line agents like erythromycin and clindamycin, making susceptibility testing important for penicillin-allergic patients 5

Common Pitfalls to Avoid

• Failure to report GBS in urine specimens from pregnant women can lead to missed opportunities for intrapartum prophylaxis 1
• Attempting to eradicate GBS colonization before labor with antibiotics is ineffective as a strategy to prevent the need for intrapartum prophylaxis 2
• Withholding intrapartum prophylaxis for women with history of GBS bacteriuria in the current pregnancy, even if subsequent cultures are negative, is not recommended 2
• Urine specimens from pregnant patients should be clearly labeled to indicate pregnancy status to assist laboratory processing and appropriate reporting of results 1