What is the recommended treatment for a Group B strep (Streptococcus agalactiae) urinary tract infection (UTI)?

Treatment of Group B Streptococcus Urinary Tract Infection

First-Line Treatment Recommendation

For non-pregnant adults with symptomatic GBS UTI, treat with ampicillin 500 mg orally every 8 hours for 3-7 days, or amoxicillin 500 mg orally every 8 hours as an equally effective alternative. 1, 2

Critical Distinction: Pregnancy Status Determines Management

Pregnant vs. Non-Pregnant Patients:

• Pregnant women: Any concentration of GBS bacteriuria (regardless of CFU count or symptoms) mandates both immediate treatment of the UTI AND intrapartum antibiotic prophylaxis during labor with penicillin G 5 million units IV initially, then 2.5-3.0 million units IV every 4 hours until delivery. 1, 2, 3

• Non-pregnant adults: Treat only if symptomatic or if bacteriuria is ≥50,000 CFU/mL with abnormal urinalysis. Asymptomatic bacteriuria in non-pregnant patients should NOT be treated. 1, 4

This distinction is critical because the CDC guidelines for universal GBS treatment apply specifically to prevent neonatal disease and do not apply to non-pregnant individuals. 4

Treatment Algorithm by Clinical Severity

Uncomplicated UTI (non-pregnant):

• Ampicillin 500 mg PO every 8 hours for 3-7 days 1, 2
• Alternative: Amoxicillin 500 mg PO every 8 hours for 3-7 days 1, 2
• All GBS strains remain fully sensitive to penicillin and ampicillin 5

Complicated UTI or Severe Infection:

• Escalate to ampicillin 18-30 g/day IV in divided doses 1, 2
• Alternative: Penicillin G 5 million units IV initially, then 2.5 million units IV every 4 hours 1
• Consider initial IV therapy with ampicillin 2 g IV every 4-6 hours, then transition to oral therapy once clinically stable 4
• Duration: 5-7 days for complicated UTI, 10-14 days for severe infections or bacteremia 1, 2

Men with possible prostatitis:

• Extend treatment duration to 14 days to ensure adequate coverage 4

Penicillin-Allergic Patients

Non-severe penicillin allergy:

• Cefazolin 2 g IV initial dose, then 1 g IV every 8 hours 1, 2
• Oral alternative: Cephalexin 1

Severe penicillin allergy:

• Clindamycin 900 mg IV every 8 hours OR 300-450 mg PO every 6-8 hours 2, 4
• Critical caveat: Clindamycin resistance is extremely high (77.34% in recent studies), so susceptibility testing is mandatory before use. 2, 5
• Vancomycin may be considered for severe infections with significant beta-lactam allergies 2

Essential Clinical Considerations

Obtain urine culture before treatment:

• Confirm diagnosis with culture showing ≥50,000 CFU/mL 1, 2
• Significant bacteriuria is defined as ≥50,000 CFU/mL of a single urinary pathogen 1, 2

Distinguish colonization from infection:

• Asymptomatic bacteriuria in non-pregnant patients should NOT be treated to prevent antibiotic resistance 1, 4
• Treatment of asymptomatic bacteriuria leads to unnecessary antibiotic exposure, resistance development, and potential adverse effects without clinical benefit 4

Pregnancy-specific management:

• Women with documented GBS bacteriuria in pregnancy should NOT be re-screened in the third trimester, as they are presumed colonized 3
• Fluoroquinolones must be avoided in pregnant patients 2

Common Pitfalls to Avoid

Underdosing or premature discontinuation:

• Leads to treatment failure and recurrence 1
• Ensure full course completion based on infection severity

Using clindamycin without susceptibility testing:

• High resistance rates (77.34%) make empiric use dangerous 1, 5
• Always confirm susceptibility before prescribing

Failing to provide intrapartum prophylaxis in pregnancy:

• Any GBS bacteriuria during pregnancy requires intrapartum prophylaxis to prevent neonatal mortality 1, 3

Treating asymptomatic bacteriuria in non-pregnant patients:

• This promotes antibiotic resistance without clinical benefit 1, 4
• Only treat symptomatic infections or significant bacteriuria with abnormal urinalysis

Overlooking complicated infections:

• GBS can cause rare but serious complications including abdominopelvic abscesses, particularly in diabetic patients 6
• Consider imaging if severe abdominal/pelvic pain accompanies UTI symptoms

Monitoring and Follow-Up

• Consider follow-up urine culture after treatment completion to ensure eradication, especially in complicated cases or recurrent UTIs 2, 4
• For complicated infections or when structural abnormalities are suspected, evaluation of the urinary tract may be indicated 2