Treatment of Streptococcus agalactiae (Group B Streptococcus) UTI
For non-pregnant adults with symptomatic GBS UTI, treat with penicillin or ampicillin for 7-10 days, as GBS remains universally susceptible to beta-lactams and these narrow-spectrum agents minimize collateral resistance. 1
First-Line Treatment Options
Penicillin G is the preferred agent due to its narrow spectrum of activity 1:
- Dosing: 500 mg orally every 6-8 hours for 7-10 days 1
- GBS demonstrates 100% susceptibility to penicillin with no resistance reported 2, 3
Ampicillin is an acceptable alternative 1, 4:
- Dosing: 500 mg orally every 8 hours for 7-10 days 1
- FDA-approved dosing for genitourinary infections: 500 mg four times daily 4
- Demonstrates >95% susceptibility in clinical studies 2, 5
- Should be administered at least 30 minutes before or 2 hours after meals for maximal absorption 4
Penicillin-Allergic Patients
For patients with documented penicillin allergy 1:
- Clindamycin: 300-450 mg orally every 8 hours 1
- Critical caveat: Susceptibility testing must be performed before use due to increasing resistance patterns 1
- Alternative options include cephalothin (100% susceptibility) or erythromycin (>95% susceptibility), though resistance to erythromycin is emerging 2, 5
Avoid fluoroquinolones despite their activity, as resistance rates are concerning (12.8% in recent studies, particularly in men and non-pregnant women) 3
Treatment Duration and Monitoring
Duration: 7-10 days is standard for uncomplicated GBS UTI 1:
- Treatment should continue for a minimum of 48-72 hours after the patient becomes asymptomatic 4
- For complicated infections or when prostatitis cannot be excluded in men, extend to 14 days 6
Follow-up: Post-treatment urine culture is warranted to ensure eradication, especially in patients with recurrent UTIs 1
Special Considerations for Complicated UTI
If the patient presents with systemic symptoms or complicated UTI 6:
- Consider initial IV therapy with ampicillin 2 g IV every 4-6 hours, then transition to oral therapy once clinically stable 6
- Combination therapy with ampicillin plus an aminoglycoside may be appropriate for severe presentations 6
- Address any underlying urological abnormalities, as GBS UTIs are frequently associated with comorbidities, particularly diabetes mellitus 3
Critical Pitfalls to Avoid
Do not confuse pregnancy guidelines with non-pregnant patient management: The CDC guidelines mandating treatment of all GBS bacteriuria apply specifically to pregnant women to prevent neonatal disease and should not be applied to non-pregnant patients 1. In non-pregnant adults, treat only if symptomatic or if underlying urinary tract abnormalities exist 1.
Identify and treat reservoirs: GBS can colonize the vagina, urethra, and gastrointestinal tract 2. In women with recurrent infections, consider vaginal lavages with 2% chlorhexidine solution in addition to systemic antibiotics 2, 7.
Avoid tetracycline and co-trimoxazole: These agents show high resistance rates (81.6% and 68.9% respectively) and should not be used empirically 5