Treatment of Group B Streptococcus (GBS) Urinary Tract Infections
For GBS urinary tract infections in pregnant women, treat with standard UTI antibiotics according to susceptibility testing AND provide intrapartum antibiotic prophylaxis during labor regardless of prior treatment, using penicillin G or ampicillin as first-line agents. 1
First-Line Treatment for GBS UTI
Non-Pregnant Patients
- Penicillin remains the preferred agent due to its narrow spectrum and high efficacy against GBS, though specific dosing for outpatient UTI treatment should follow standard UTI protocols 1, 2
- Ampicillin is an acceptable alternative for GBS UTI treatment 1
- Nitrofurantoin is specifically recommended for patients with GBS bacteriuria and can be used as an effective oral option 3
Pregnant Patients - Critical Distinction
- Any GBS detected in urine during pregnancy (symptomatic or asymptomatic UTI) requires TWO interventions: 4, 1
Common pitfall: Treating the UTI during pregnancy does NOT eliminate the need for intrapartum prophylaxis—women with GBS bacteriuria at any point in pregnancy still require prophylaxis during labor to prevent early-onset neonatal GBS disease 1
Treatment for Penicillin-Allergic Patients
Low Risk for Anaphylaxis
- Cefazolin is the preferred alternative (2 g IV initial dose, then 1 g IV every 8 hours for inpatient treatment) 1, 2
- Oral cephalosporins like cephalexin can be considered for outpatient UTI treatment 3
High Risk for Anaphylaxis
- Clindamycin (900 mg IV every 8 hours) ONLY if the GBS isolate is confirmed susceptible to both clindamycin and erythromycin 4, 1, 2
- Vancomycin (1 g IV every 12 hours) if susceptibility testing is unavailable or the isolate shows resistance 1, 2
Critical caveat: Clindamycin resistance rates have increased to 3-15% in the US, and erythromycin resistance can reach 20.2%, making susceptibility testing mandatory before using clindamycin 2, 5
Importance of Susceptibility Testing
- Always perform susceptibility testing on GBS isolates from penicillin-allergic patients at high risk for anaphylaxis 4, 1
- Test for inducible clindamycin resistance if the isolate is susceptible to clindamycin but resistant to erythromycin—the isolate may have hidden resistance despite appearing susceptible 4, 1, 2
- Recent data shows concerning resistance patterns: 19% resistance to clindamycin, 31% to azithromycin, and emerging decreased sensitivity to penicillin (15-18% showing intermediate sensitivity) 3, 6
Resistance Patterns and Clinical Implications
While GBS is still considered universally susceptible to beta-lactams, emerging data shows:
- Some isolates demonstrate reduced susceptibility to penicillin and ampicillin (8-18% showing intermediate sensitivity) 3, 6
- High resistance rates to macrolides and clindamycin make erythromycin unsuitable for empiric therapy 4, 2, 5
- All isolates remain susceptible to vancomycin in most studies, though two documented cases of vancomycin resistance exist globally 5, 6
Key Clinical Pitfalls to Avoid
Do not treat asymptomatic GBS vaginal colonization outside of labor—antimicrobials before the intrapartum period do not eliminate carriage and promote resistance 1
Do not assume prior UTI treatment eliminates the need for intrapartum prophylaxis—any GBS bacteriuria during pregnancy mandates prophylaxis during labor regardless of earlier treatment 4, 1
Do not use clindamycin without confirmed susceptibility—resistance rates are too high for empiric use in penicillin-allergic patients 2, 5
Avoid underdosing or premature discontinuation—complete the full antibiotic course to prevent treatment failure and recurrence 1
For pregnant women, ensure coordination between outpatient and inpatient providers—documentation of GBS bacteriuria must be communicated to labor and delivery teams 1