What is the treatment for a urinary tract infection with 10,000 to 49,000 colony-forming units (CFU) of group B streptococcus (GBS) in the urine culture?

Treatment of Group B Streptococcus in Urine Culture with 10,000-49,000 CFU

Group B Streptococcus (GBS) detected in urine at any colony count (including 10,000-49,000 CFU) requires appropriate antibiotic treatment if symptomatic, and all pregnant women with GBS bacteriuria require intrapartum antibiotic prophylaxis regardless of prior treatment. 1

Treatment Approach Based on Patient Population

For Pregnant Women

1. Acute UTI Treatment:

   • Treat symptomatic GBS bacteriuria with appropriate antibiotics for 7-14 days 1
   • First-line options:
     • Penicillin G or Ampicillin (preferred agents)
     • Cefazolin (for non-severe penicillin allergy)

2. Intrapartum Prophylaxis:

   • Required for all pregnant women with GBS bacteriuria during pregnancy, regardless of:

     • Colony count (even low counts of 10,000-49,000 CFU)
     • Whether treatment was given earlier in pregnancy
     • Symptoms 1

   • Recommended regimens:

     • Penicillin G: 5 million units IV initial dose, then 2.5-3.0 million units IV every 4 hours until delivery
     • Ampicillin: 2 g IV initial dose, then 1 g IV every 4 hours until delivery
     • For penicillin allergy: Cefazolin, clindamycin, or vancomycin based on sensitivity testing 1

3. Important Considerations:

   • No need to re-screen women with documented GBS bacteriuria by genital tract or urinary culture in the third trimester 2
   • Communicate GBS status to all providers involved in care, particularly those managing labor and delivery 1

For Non-Pregnant Adults

1. Treatment Selection:

   • Base antibiotic choice on susceptibility testing

   • Common effective options:

     • Cephalothin (100% sensitivity reported)
     • Norfloxacin (96.9% sensitivity)
     • Ampicillin (96% sensitivity)
     • Nitrofurantoin (95.5% sensitivity)
     • Vancomycin (95% sensitivity) 3

   • Avoid:

     • Tetracycline (81.6% resistance)
     • Co-trimoxazole (68.9% resistance) 3

2. Duration of Treatment:

   • Standard duration: 7-14 days 1
   • Consider longer treatment for complicated UTIs

Clinical Considerations and Risk Assessment

Risk Factors for Complications

• Urinary tract abnormalities (present in 60% of non-pregnant adults with GBS UTI) 4
• Chronic renal failure (27% of non-pregnant adults with GBS UTI) 4
• Immunocompromised status
• Diabetes
• Liver disease 1

Monitoring and Follow-up

• For patients with GBS bacteremia:
  • Obtain follow-up blood cultures to document clearance
  • Consider echocardiography to rule out endocarditis
  • Consider imaging to identify potential metastatic foci of infection 1
  • Remove infected catheters if present 1

Important Clinical Pearls

• GBS UTIs have a significantly lower rate of progression to pyelonephritis (1.1%) compared to E. coli UTIs (15.6%) 5
• GBS in urine may signal underlying urinary tract abnormalities that warrant screening 4
• Despite lower colony counts (10,000-49,000 CFU/mL), GBS should not be dismissed as contamination, especially in pregnant women 1, 2
• Asymptomatic non-pregnant patients with low colony counts may not require treatment unless they have specific risk factors 2

Antibiotic Resistance Considerations

• Recent studies show emerging resistance patterns:
  • Some regions report resistance to penicillin (18.3%), ampicillin (81.6%), clindamycin (23.3%), and vancomycin (30%) 6
  • Consider local resistance patterns when selecting empiric therapy
  • Adjust treatment based on susceptibility testing when available

Remember that while low colony counts of GBS (10,000-49,000 CFU/mL) might be considered less significant for other bacteria, for GBS—especially in pregnant women—they warrant appropriate treatment and prophylaxis to prevent serious maternal and neonatal complications.