What is the recommended treatment for a non-pregnant adult with a Group B strep urinary tract infection?

Treatment of Group B Streptococcus UTI in Non-Pregnant Adults

For symptomatic non-pregnant adults with Group B Streptococcus urinary tract infection, treat with ampicillin 500 mg orally every 8 hours or amoxicillin 500 mg orally every 8 hours for 7-10 days. 1

Critical First Step: Confirm Symptomatic Infection

• Do not treat asymptomatic GBS bacteriuria in non-pregnant patients - this represents colonization that should not receive antibiotics, as treatment leads to unnecessary antibiotic exposure, resistance development, and adverse effects without clinical benefit 2
• Only treat if the patient has dysuria, frequency, urgency, suprapubic pain, fever, flank pain, or other UTI symptoms combined with pyuria (positive leukocyte esterase, WBCs in urine) 2
• The distinction between pregnancy and non-pregnancy status is critical: pregnant women require treatment of any GBS bacteriuria regardless of symptoms, but non-pregnant patients require symptoms plus laboratory evidence of infection 2, 1

First-Line Antibiotic Regimens

Uncomplicated UTI (3-7 days)

• Ampicillin 500 mg orally every 8 hours for 3-7 days 1
• Amoxicillin 500 mg orally every 8 hours for 3-7 days (equally effective alternative) 1, 3
• Penicillin G 500 mg orally every 6-8 hours for 7-10 days (preferred by CDC due to narrow spectrum) 2

Complicated UTI or Severe Infection (5-14 days)

• Ampicillin 18-30 g/day IV in divided doses for severe presentations 1
• Penicillin G 5 million units IV initially, then 2.5 million units IV every 4 hours for severe infections 1
• Consider extending treatment to 14 days for complicated infections or when prostatitis cannot be excluded in men 2
• For bacteremia or severe systemic symptoms: 10-14 days of therapy 1

Penicillin-Allergic Patients

Non-High-Risk Allergy

• Cefazolin 2 g IV initial dose, then 1 g IV every 8 hours 1
• Cephalexin orally as an alternative 1

High-Risk Allergy (History of Anaphylaxis)

• Clindamycin 300-450 mg orally every 8 hours - but only after susceptibility testing confirms susceptibility, as resistance ranges from 3-15% 2, 1
• Vancomycin 1 g IV every 12 hours if clindamycin resistance or susceptibility unknown 1

Key Clinical Considerations

• All GBS isolates remain universally susceptible to penicillin - penicillin G, ampicillin, and amoxicillin are all appropriate first-line agents 4, 5
• Obtain urine culture before initiating therapy to confirm diagnosis, with significant bacteriuria defined as ≥50,000 CFU/mL 1
• GBS accounts for approximately 2% of positive urine cultures in non-pregnant adults, with 85% occurring in women 6
• Underlying urinary tract abnormalities are present in 60% of cases, and chronic renal failure in 27% 6

Follow-Up and Monitoring

• Follow-up urine culture after treatment completion may be warranted to ensure eradication, especially in patients with recurrent UTIs 2
• Screen for underlying urinary tract abnormalities when GBS UTI is identified, as 60% of patients have structural abnormalities 6
• Clinical outcome may be poor in 18% of episodes despite appropriate treatment 6

Common Pitfalls to Avoid

• Never use clindamycin empirically without susceptibility testing - resistance rates are increasing (3-15%) and treatment failure is common with resistant strains 2, 1
• Do not undertreat or discontinue prematurely - this leads to treatment failure and recurrence 1
• Avoid treating asymptomatic bacteriuria - this is the most common error and leads to unnecessary antibiotic resistance without clinical benefit 2
• Do not confuse non-pregnant management with pregnancy protocols - pregnant women require treatment of any GBS bacteriuria plus intrapartum prophylaxis, but non-pregnant patients only need treatment if symptomatic 2, 1