What is the recommended treatment for Group B streptococcal (GBS) urinary tract infections (UTI)?

Treatment of Group B Streptococcal Urinary Tract Infections

Penicillin G or ampicillin should be used as first-line therapy for Group B Streptococcal (GBS) urinary tract infections due to their narrow spectrum of activity and lower likelihood of selecting for resistant organisms. 1

First-Line Treatment Options

For Hospitalized Patients (IV Therapy)

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

For Outpatient Treatment (Oral Therapy)

• Amoxicillin: 500 mg every 8 hours or 875 mg every 12 hours for 7-10 days 2
• Nitrofurantoin: Effective for uncomplicated lower UTIs caused by GBS 1, 3

Alternative Treatment for Penicillin-Allergic Patients

Non-Anaphylactic Allergy

• Cefazolin: 2 g IV initial dose, then 1 g IV every 8 hours 1
• Cephalexin (oral): For outpatient treatment 4

Anaphylactic Allergy

• Clindamycin: 900 mg IV every 8 hours (only if susceptibility testing confirms sensitivity) 1
• Vancomycin: 1 g IV every 12 hours (for clindamycin-resistant strains) 1

Treatment Duration

• Uncomplicated UTIs: 7-10 days 1
• Complicated UTIs or pyelonephritis: 10-14 days 1
• Continue treatment for at least 48-72 hours after the patient becomes asymptomatic 2

Special Considerations for GBS UTIs in Pregnancy

GBS bacteriuria during pregnancy requires special attention as it indicates heavy genital tract colonization and increases the risk of adverse pregnancy outcomes:

1. Immediate treatment of the current UTI with appropriate antibiotics 1
2. Intrapartum antibiotic prophylaxis during labor regardless of whether treatment was provided earlier in pregnancy 1
3. Post-treatment urine culture to confirm eradication of infection 1
4. No need for vaginal-rectal screening at 35-37 weeks for women with GBS bacteriuria during pregnancy 1

Antibiotic Resistance Considerations

• All GBS isolates remain susceptible to penicillin, ampicillin, cefazolin, and vancomycin 1
• Resistance to alternative agents is increasing:
  • 31% of isolates may be resistant to azithromycin and ceftriaxone 3
  • 19% to clindamycin 3
  • Erythromycin is no longer recommended due to increasing resistance 1

Clinical Pearls and Pitfalls

Pearls

• GBS UTIs are less likely to progress to pyelonephritis compared to E. coli UTIs (1.1% vs 15.6%) 5
• Nitrofurantoin is particularly effective for GBS bacteriuria and has minimal impact on vaginal flora 3
• All GBS isolates remain susceptible to penicillin and ampicillin, making them excellent first-line choices 1

Pitfalls to Avoid

1. Failing to perform susceptibility testing in penicillin-allergic patients, given the high rates of resistance to alternative antibiotics 1
2. Using fluoroquinolones as first-line therapy when alternatives exist, due to FDA warnings about serious side effects 1
3. Not confirming eradication of GBS bacteriuria with follow-up cultures, especially in pregnant women 1
4. Overlooking the need for intrapartum prophylaxis in pregnant women with history of GBS bacteriuria, even if previously treated 1

Treatment Algorithm

1. Confirm diagnosis with urine culture showing GBS
2. Assess patient factors:
   • Pregnancy status
   • Penicillin allergy status
   • Severity of infection (lower UTI vs pyelonephritis)
   • Outpatient vs inpatient management
3. Select appropriate antibiotic based on above factors
4. Monitor response to therapy
5. Obtain follow-up urine culture to confirm eradication
6. For pregnant women: Plan for intrapartum antibiotic prophylaxis regardless of treatment earlier in pregnancy

By following this evidence-based approach, clinicians can effectively manage GBS UTIs while minimizing the risk of complications and antibiotic resistance.