Treatment of Group B Streptococcus Urinary Tract Infections
Penicillin G is the preferred first-line treatment for GBS UTI due to its narrow spectrum and high efficacy, with ampicillin as an acceptable alternative. 1, 2
Treatment Approach Based on Pregnancy Status
For Pregnant Women
Any concentration of GBS in urine during pregnancy requires intrapartum antibiotic prophylaxis during labor, regardless of colony count. 3, 1, 4
- GBS bacteriuria at any point in pregnancy is a marker for heavy genital tract colonization and increases risk for early-onset neonatal disease 3
- Do not treat GBS bacteriuria with antibiotics during pregnancy outside of labor, as recolonization typically occurs after treatment 3, 4
- Intrapartum prophylaxis with penicillin, ampicillin, or cefazolin for ≥4 hours before delivery is 78% effective in preventing early-onset GBS disease 3
- Women with documented GBS bacteriuria should not be re-screened in the third trimester, as they are presumed colonized 4
For Non-Pregnant Adults
Treat symptomatic non-pregnant patients with GBS UTI according to standard UTI protocols; asymptomatic bacteriuria does not require treatment. 2
- The CDC guidelines for universal treatment of any GBS concentration apply specifically to pregnant women and should not be applied to non-pregnant patients 2
- Treatment is indicated only if the patient is symptomatic or has underlying urinary tract abnormalities 2
Specific Antibiotic Regimens
First-Line Options (Non-Allergic Patients)
- Penicillin G: 500 mg orally every 6-8 hours for 7-10 days 2
- Ampicillin: 500 mg orally every 8 hours for 7-10 days 2, 5
- For severe infections requiring IV therapy: Penicillin G 5 million units IV initially, then 2.5 million units IV every 4 hours 6
Penicillin-Allergic Patients
For low-risk penicillin allergy (no anaphylaxis history), use cefazolin or cephalexin as the preferred alternative. 1, 6
For high-risk anaphylaxis patients, clindamycin 300-450 mg orally every 8 hours is preferred, but only after susceptibility testing confirms susceptibility. 1, 2, 6
- Approximately 20% of GBS isolates are resistant to clindamycin, making susceptibility testing mandatory before use 1
- Test for inducible clindamycin resistance (D-test) if the isolate is erythromycin-resistant but clindamycin-susceptible 1, 6
- Vancomycin 1 g IV every 12 hours is reserved for severe infections or when susceptibility results are unavailable 6
Duration and Monitoring
- Complete the full 7-10 day course to ensure eradication and prevent recurrence 1, 2
- Follow-up urine culture after treatment may be warranted in patients with recurrent UTIs 2
- For chronic or stubborn infections, treatment for several weeks may be required 5
Critical Pitfalls to Avoid
- Underdosing or premature discontinuation leads to treatment failure and recurrence 1, 6
- Using clindamycin without susceptibility testing risks treatment failure due to resistance 1, 7
- Treating asymptomatic GBS bacteriuria in non-pregnant patients is unnecessary and promotes antibiotic resistance 2
- Failing to provide intrapartum prophylaxis to pregnant women with any GBS bacteriuria increases neonatal mortality risk 3, 4
- Penicillin carries a 5 per 10,000 risk of anaphylaxis, requiring careful allergy history assessment 8