Antibiotic Treatment for Group B Streptococcus UTI with 10-100M CFU
Penicillin G (5 million units IV initial dose, then 2.5-3.0 million units IV every 4 hours) or ampicillin (2 g IV initial dose, then 1 g IV every 4 hours) are the first-line treatments for Group B Streptococcus urinary tract infections with bacterial loads of 10-100 million CFU. 1
First-Line Treatment Options
Non-Pregnant Patients
- Penicillin G: 5 million units IV initial dose, then 2.5-3.0 million units IV every 4 hours
- Ampicillin: 2 g IV initial dose, then 1 g IV every 4 hours
- Treatment duration: 5-7 days for uncomplicated UTIs 2
Pregnant Patients
- Same antibiotic regimens as above
- Any colony count of GBS in urine during pregnancy is considered significant 1
- Requires intrapartum antibiotic prophylaxis during labor regardless of previous treatment 1
Alternative Options for Penicillin-Allergic Patients
Low Risk for Anaphylaxis
- Cefazolin: 2 g IV initial dose, then 1 g IV every 8 hours 2
High Risk for Anaphylaxis (history of anaphylaxis, angioedema, respiratory distress, or urticaria)
- Clindamycin: 900 mg IV every 8 hours (if isolate is susceptible to both clindamycin and erythromycin) 2, 1
- Vancomycin: 1 g IV every 12 hours (if isolate is resistant to clindamycin/erythromycin or susceptibility is unknown) 2, 1
Important Clinical Considerations
Susceptibility Testing
- GBS remains universally susceptible to penicillin 1
- Susceptibility testing is essential for penicillin-allergic patients due to increasing resistance to alternative antibiotics 1, 3
- High rates of resistance have been reported for:
- Erythromycin (36.3%)
- Clindamycin (26%)
- Tetracycline (81.5%)
- Azithromycin (44.5%) 3
Special Considerations in Pregnancy
- GBS bacteriuria at any colony count during pregnancy indicates heavy genital tract colonization 1
- Women with GBS bacteriuria during pregnancy should not be re-screened in the third trimester as they are presumed to be GBS colonized 4
- Intrapartum antibiotic prophylaxis is required during labor regardless of previous treatment 1, 5
Treatment Duration
- Uncomplicated UTIs: 5-7 days 2
- Complicated UTIs: 10-14 days 1
- Treatment should continue for at least 48-72 hours after symptoms resolve 1
Monitoring and Follow-up
- For non-pregnant patients, routine follow-up cultures are not necessary if symptoms resolve
- For pregnant patients, follow pregnancy-specific GBS protocols for intrapartum prophylaxis
- Monitor for recurrence as recolonization after treatment is common 1
Pitfalls to Avoid
- Do not use erythromycin for GBS UTIs due to high resistance rates (36.3%) 3
- Do not re-screen pregnant women with documented GBS bacteriuria by genital tract culture or urinary culture in the third trimester 4
- Do not assume treatment eliminates GBS colonization; recolonization after treatment is typical 1
- Avoid using broad-spectrum antibiotics like carbapenems unless multidrug resistance is confirmed 2
By following these evidence-based recommendations, clinicians can effectively treat GBS UTIs while minimizing the risk of treatment failure and antibiotic resistance.