Do you treat Group B Streptococcus (GBS) contaminated urine with 10-100 million Colony-Forming Units per Liter (CFU/L) as a Urinary Tract Infection (UTI) and what is the best antibiotic prescription?

Treatment of GBS in Urine with 10-100M CFU/L

For Group B Streptococcus (GBS) in urine with colony counts of 10-100 million CFU/L in non-pregnant adults, treatment is not recommended unless the patient is symptomatic, as this represents asymptomatic bacteriuria rather than a true UTI. 1, 2

Diagnostic Considerations

Asymptomatic Bacteriuria vs. UTI

• Colony counts of 10-100M CFU/L (equivalent to 10⁴-10⁵ CFU/mL) are below the traditional threshold for significant bacteriuria (≥10⁵ CFU/mL) 3
• According to the European Association of Urology (EAU), asymptomatic bacteriuria is defined as:
  • Bacterial growth >10⁵ CFU/mL in two consecutive samples in women
  • Bacterial growth >10⁵ CFU/mL in a single sample in men 1
• Patients with colony counts <100,000 CFU/mL are 73.86 times less likely to have a clinically significant UTI compared to those with counts ≥100,000 CFU/mL 3

When to Treat

Do NOT treat asymptomatic bacteriuria in:

• Women without risk factors
• Patients with well-regulated diabetes
• Postmenopausal women
• Elderly institutionalized patients
• Patients with dysfunctional/reconstructed lower urinary tract
• Renal transplant recipients
• Patients before arthroplasty surgery
• Patients with recurrent UTIs 1

DO treat GBS bacteriuria in:

• Pregnant women (regardless of colony count)
• Patients undergoing urological procedures breaching the mucosa
• Symptomatic patients with signs of active UTI 1, 2, 4

Treatment Algorithm for GBS in Urine

1. For Symptomatic UTI with GBS:

First-line treatment:

• Amoxicillin 500 mg orally every 8 hours for 7-10 days 2

Alternative options (for penicillin-allergic patients):

• Nitrofurantoin 100 mg PO every 6 hours for 7 days
• Cefazolin 1-2 g IV every 8 hours or oral cephalexin 500 mg every 6 hours (for non-severe penicillin allergy)
• Fluoroquinolones if susceptible
• Fosfomycin 3 g PO single dose for uncomplicated cases 2

2. For Asymptomatic GBS Bacteriuria:

• Do not treat unless patient is pregnant or undergoing urological procedures 1, 2
• For pregnant women: Treat at diagnosis AND provide intrapartum prophylaxis 2, 4

3. For Pregnant Women with GBS Bacteriuria:

• Treat at time of diagnosis regardless of colony count
• Provide intrapartum prophylaxis during labor:
  • 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 2, 4

Important Clinical Considerations

• GBS is highly susceptible to penicillin G 5, but resistance patterns vary regionally
• Recent studies show increasing resistance to ampicillin (81.6%), clindamycin (23.3%), and even penicillin (18.3%) in some regions 6
• Discontinue antimicrobial therapy within 24 hours after symptoms resolve to prevent resistance development 2
• Do not re-screen pregnant women with documented GBS bacteriuria by genital tract culture or urinary culture in the third trimester, as they are presumed to be GBS colonized 4

Common Pitfalls to Avoid

1. Overtreating asymptomatic bacteriuria: Treating non-significant bacteriuria leads to unnecessary antibiotic use and promotes resistance 1, 3
2. Using inappropriate antibiotics: Newer azole agents and echinocandins achieve poor urine concentrations and should not be used for UTIs 7
3. Misinterpreting low colony counts: Colony counts <100,000 CFU/mL are often not clinically significant in non-pregnant adults 3
4. Failing to recognize special populations: Pregnant women require treatment of GBS bacteriuria regardless of colony count or symptoms 2, 4

Remember that GBS in urine may represent urethral or vaginal contamination rather than true UTI, especially at lower colony counts. Focus on treating symptomatic patients and special populations while avoiding unnecessary antibiotic use in asymptomatic individuals.