Outpatient Treatment for Group B Streptococcus UTI in Non-Pregnant Adults
For non-pregnant adults with Group B Streptococcus urinary tract infection, treat with amoxicillin 500 mg orally every 8 hours for 3-7 days, or ampicillin 500 mg orally every 8 hours for 3-7 days as first-line therapy. 1
First-Line Treatment Regimens
Amoxicillin 500 mg orally every 8 hours is the preferred first-line agent for uncomplicated GBS UTI, with treatment duration of 3-7 days depending on symptom severity and clinical response 1, 2
Ampicillin 500 mg orally every 8 hours is an equally effective alternative for uncomplicated GBS UTI, also given for 3-7 days 1
Both agents demonstrate universal susceptibility against GBS, as all beta-hemolytic streptococci are predictably susceptible to penicillin and other beta-lactams 3
Treatment Duration Based on Infection Complexity
Uncomplicated UTI: 3-7 days of oral therapy is sufficient 1
Complicated UTI (presence of urinary tract abnormalities, chronic renal failure, diabetes mellitus, or recurrent infections): 5-7 days of therapy is recommended 1
Severe infections or bacteremia: 10-14 days of therapy, often requiring initial IV treatment 1
Alternative Regimens for Penicillin-Allergic Patients
For non-severe penicillin allergies: Cefazolin 2 g IV initial dose, then 1 g IV every 8 hours can be used, though this requires intravenous access and is typically reserved for inpatient settings 1
For severe penicillin allergies: Clindamycin 300-450 mg orally every 6 hours may be considered, but only if the GBS isolate is confirmed susceptible through antimicrobial susceptibility testing 1
Clindamycin resistance ranges from 3-15% among GBS isolates, making susceptibility testing mandatory before use 3
Vancomycin may be considered for severe infections in patients with significant beta-lactam allergies, but requires IV administration 1
Critical Clinical Considerations
Obtain urine culture before initiating therapy to confirm the diagnosis and guide treatment, as recommended by the Infectious Diseases Society of America 1, 2
Significant bacteriuria is defined as ≥50,000 CFUs/mL of a single urinary pathogen 1
GBS accounts for approximately 2% of positive urine cultures in non-pregnant adults and signals a need for screening for urinary tract abnormalities 4
Screen for underlying conditions: 95% of patients with GBS UTI have at least one underlying condition, most commonly urinary tract abnormalities (60%) and chronic renal failure (27%) 4
Diabetes mellitus significantly increases risk for invasive GBS urogenital infections and should be evaluated 5
Important Pitfalls to Avoid
Do not treat asymptomatic bacteriuria in non-pregnant patients: GBS bacteriuria at 10,000-49,000 CFU/mL in asymptomatic non-pregnant patients represents asymptomatic bacteriuria that should not be treated, as this leads to unnecessary antibiotic exposure and resistance development without clinical benefit 3
Distinguish colonization from true infection: Only treat symptomatic patients or those with underlying urinary tract abnormalities 1
Avoid gentamicin: All GBS isolates in one study were resistant to gentamicin, making it an inappropriate choice 4
Do not use fluoroquinolones in pregnancy: If pregnancy status is uncertain, avoid fluoroquinolones until pregnancy is ruled out 3
Follow-Up and Monitoring
Consider follow-up urine culture after completion of treatment to ensure eradication, especially in complicated cases or patients with underlying urinary tract abnormalities 1
The clinical outcome was poor in 18% of episodes despite treatment in one study, emphasizing the importance of follow-up 4
Evaluate for structural urinary tract abnormalities in patients with recurrent GBS UTI, as GBS presence signals a need for screening 4