What is the recommended treatment and management for a urinary tract infection caused by beta‑hemolytic group B Streptococcus (Streptococcus agalactiae)?

Treatment of Group B Streptococcus (GBS) Urinary Tract Infection

For non-pregnant adults with symptomatic GBS UTI, treat with penicillin or ampicillin for 7-10 days; for asymptomatic bacteriuria in non-pregnant patients, do not treat unless undergoing urologic procedures with mucosal trauma. 1

Critical First Step: Determine Pregnancy Status

The management of GBS bacteriuria is fundamentally different based on pregnancy status, making this the most important clinical distinction 1, 2:

• If pregnant: Any concentration of GBS in urine requires immediate treatment PLUS mandatory intrapartum IV antibiotic prophylaxis during labor, regardless of symptoms or when the UTI was treated 2
• If not pregnant: Treatment is only indicated for symptomatic UTI or specific high-risk scenarios 1

Management for Non-Pregnant Adults

When to Treat

Treat GBS bacteriuria in non-pregnant patients only if: 1

• Patient has genitourinary symptoms (dysuria, frequency, urgency, flank pain, fever)
• Patient is undergoing endoscopic urologic procedures with mucosal trauma 3
• Patient has underlying urinary tract abnormalities 1

When NOT to Treat

Do not treat asymptomatic bacteriuria (ASB) in non-pregnant patients, even with positive GBS culture: 3, 1

• Patients with diabetes mellitus 3
• Elderly or institutionalized patients 3
• Patients with indwelling catheters (short-term or long-term) 3
• Patients with neurogenic bladder on intermittent catheterization 3
• Patients before non-urologic surgery (including orthopedic/arthroplasty) 3
• Patients with recurrent UTIs 3

The 2019 IDSA guidelines provide strong evidence that treating ASB leads to unnecessary antibiotic exposure, resistance development, and adverse effects without clinical benefit 1. This represents a strong recommendation based on moderate-quality evidence 3.

Antibiotic Selection for Symptomatic Non-Pregnant Patients

First-line therapy: 1, 4

• Penicillin G: 500 mg orally every 6-8 hours for 7-10 days
• Ampicillin: 500 mg orally every 6 hours for 7-10 days 4

GBS demonstrates universal susceptibility to penicillin and beta-lactams, with >95% susceptibility to ampicillin documented across studies 5, 6, 7.

For penicillin-allergic patients: 1

• Clindamycin: 300-450 mg orally every 8 hours for 7-10 days
• Obtain susceptibility testing before use, as clindamycin resistance ranges from 3-15% 1, 7

Alternative agents with documented efficacy: 5, 6

• Cephalosporins (cephalothin): 100% susceptibility
• Nitrofurantoin: 95.5% susceptibility
• Norfloxacin: 96.9% susceptibility

Avoid: 5, 6

• Tetracycline (81.6% resistance)
• Co-trimoxazole (68.9% resistance)

Duration and Monitoring

• Standard duration: 7-10 days for uncomplicated cystitis 1
• Extended duration: 14 days for complicated infections or when prostatitis cannot be excluded in men 1
• Follow-up culture: Consider post-treatment urine culture in patients with recurrent UTIs to ensure eradication 1

Management for Pregnant Patients

Immediate Treatment Requirements

All pregnant women with ANY concentration of GBS in urine must receive: 2

1. Immediate treatment of the acute UTI using pregnancy-safe antibiotics
2. Mandatory intrapartum IV antibiotic prophylaxis during labor, regardless of whether the UTI was treated earlier in pregnancy

This dual requirement exists because GBS bacteriuria indicates heavy genital tract colonization and significantly increases the risk of early-onset neonatal GBS disease 2. Treating the UTI does NOT eliminate colonization—recolonization after oral antibiotics is typical 2.

Acute UTI Treatment in Pregnancy

First-line oral regimens for acute symptomatic UTI: 2

• Ampicillin 500 mg orally every 6 hours
• Amoxicillin 500 mg orally every 8 hours
• Cephalexin 500 mg orally every 6 hours

Duration: 7-10 days for uncomplicated UTI 2

Intrapartum Prophylaxis Regimens (During Labor)

For women without penicillin allergy: 2

• Preferred: Penicillin G 5 million units IV initially, then 2.5-3.0 million units IV every 4 hours until delivery
• Alternative: Ampicillin 2 g IV initially, then 1 g IV every 4 hours until delivery

For women with penicillin allergy (not high-risk for anaphylaxis): 2

• Cefazolin: 2 g IV initially, then 1 g IV every 8 hours until delivery

For women at high risk for anaphylaxis: 2

• If GBS susceptible to clindamycin: Clindamycin 900 mg IV every 8 hours until delivery
• If resistant or susceptibility unknown: Vancomycin 1 g IV every 12 hours until delivery

High-risk allergy features include history of anaphylaxis, angioedema, urticaria, or asthma that would make anaphylaxis more dangerous 2.

Critical Timing

Intrapartum prophylaxis must be administered ≥4 hours before delivery for maximum effectiveness, achieving 78% reduction in early-onset neonatal GBS disease 2. Even shorter durations provide some benefit, but optimal protection requires the full 4-hour window 2.

Special Pregnancy Scenarios

Preterm labor (<37 weeks): 2

• Initiate GBS prophylaxis immediately at hospital admission
• Discontinue if patient is not in true labor

Preterm premature rupture of membranes (PPROM): 2

• Ampicillin 2 g IV once, followed by 1 g IV every 6 hours for at least 48 hours
• This regimen provides both latency prolongation and adequate GBS prophylaxis

Important: Women with documented GBS bacteriuria at any point during pregnancy should NOT be re-screened with vaginal-rectal cultures at 35-37 weeks—they are presumed colonized and automatically qualify for intrapartum prophylaxis 2.

Common Clinical Pitfalls

Do not treat asymptomatic bacteriuria in non-pregnant patients: 3, 1

The most common error is treating positive urine cultures in asymptomatic patients. This practice increases antimicrobial resistance, causes adverse drug effects, and provides no clinical benefit. The 2019 IDSA guidelines make a strong recommendation against this practice based on high-quality evidence of harm 3.

Do not assume oral antibiotics eliminate GBS colonization in pregnancy: 2

Treating a GBS UTI during pregnancy does NOT eliminate the need for intrapartum prophylaxis. This is a dangerous and common misconception. Recolonization after oral antibiotics is typical, which is why IV prophylaxis during labor remains mandatory 2.

Do not use oral antibiotics for asymptomatic GBS vaginal colonization: 2

Oral or IV antibiotics given before labor are completely ineffective at eliminating GBS colonization and should never be used for asymptomatic vaginal colonization outside the intrapartum period 2.

Obtain susceptibility testing for penicillin-allergic pregnant patients: 2

For pregnant women at high risk for anaphylaxis, clindamycin and erythromycin susceptibility testing must be performed immediately, as resistance rates are significant (clindamycin 3-15%, erythromycin 7-21%) 2, 7.

Catheter-Associated Considerations

For patients with indwelling catheters: 3

• Do NOT screen for or treat catheter-associated asymptomatic bacteriuria (CA-ASB) in patients with short-term or long-term catheters (strong recommendation, level A-I evidence)
• Exceptions: pregnant women and patients undergoing urologic procedures with anticipated mucosal bleeding 3
• If catheter has been in place ≥2 weeks and symptomatic CA-UTI develops, replace catheter before initiating antimicrobial therapy 3