What is the appropriate treatment for a urinary tract infection caused by Group B Streptococcus (Streptococcus agalactiae)?

Treatment of Group B Streptococcus Urinary Tract Infection

Critical First Question: Is the Patient Pregnant?

Management of GBS UTI depends entirely on pregnancy status, as treatment goals and approaches differ fundamentally between pregnant and non-pregnant patients. 1

---

For Pregnant Women

Immediate Treatment Required

All pregnant women with any concentration of GBS in urine must receive immediate antibiotic treatment of the UTI plus mandatory intravenous intrapartum antibiotic prophylaxis during labor, regardless of symptoms, colony count, or trimester. 1, 2

• GBS bacteriuria at any level during pregnancy indicates heavy genital tract colonization and significantly increases the risk of early-onset neonatal GBS disease 1
• Treating the acute UTI does NOT eliminate GBS colonization from the genitourinary tract—recolonization after oral antibiotics is typical 1
• This is why intrapartum IV prophylaxis remains mandatory even if the UTI was treated earlier in pregnancy 1

Treatment for Acute UTI (Outpatient)

First-line options for symptomatic UTI treatment:

• Penicillin G 500 mg orally every 6-8 hours for 7-10 days (preferred due to narrow spectrum) 3, 2
• Ampicillin 500 mg orally every 8 hours for 7-10 days (acceptable alternative) 3, 2

For penicillin-allergic patients:

• Clindamycin 300-450 mg orally every 8 hours for 7-10 days (requires susceptibility testing due to 13-25% resistance rates) 4, 5, 6

Mandatory Intrapartum Prophylaxis During Labor

All pregnant women with documented GBS bacteriuria at any point in pregnancy must receive IV antibiotics during active labor, administered ≥4 hours before delivery for maximum effectiveness (78% reduction in early-onset neonatal GBS disease). 1, 2

For women without penicillin allergy:

• Penicillin G 5 million units IV initially, then 2.5-3.0 million units IV every 4 hours until delivery (preferred) 1, 2
• Ampicillin 2 g IV initially, then 1 g IV every 4 hours until delivery (acceptable alternative) 1, 2

For women with low-risk penicillin allergy (no history of anaphylaxis, angioedema, respiratory distress, or urticaria):

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

For women with high-risk penicillin allergy:

• Obtain clindamycin and erythromycin susceptibility testing immediately 1
• If susceptible to both: Clindamycin 900 mg IV every 8 hours until delivery 1, 2
• If resistant or susceptibility unknown: Vancomycin 1 g IV every 12 hours until delivery 1, 2
• Perform D-zone testing on isolates that are erythromycin-resistant but clindamycin-susceptible to detect inducible clindamycin resistance 1, 2

Special Pregnancy Scenarios

Preterm labor (<37 weeks):

• Administer GBS prophylaxis immediately at hospital admission 1
• Discontinue if patient is not in true labor 1

Preterm premature rupture of membranes (PPROM):

• Ampicillin 2 g IV once, followed by 1 g IV every 6 hours for at least 48 hours (adequate for both latency and GBS prophylaxis) 1

Critical Pitfall to Avoid in Pregnancy

Never assume that treating the UTI eliminates the need for intrapartum prophylaxis—this is a common and dangerous error that increases neonatal mortality risk. 1, 2

---

For Non-Pregnant Patients

When Treatment IS Indicated

Treat GBS UTI in non-pregnant patients only when:

• Patient has symptomatic UTI with dysuria, frequency, urgency, or suprapubic pain 3
• Patient has abnormal urinalysis (pyuria, hematuria, positive leukocyte esterase) 3
• Patient is scheduled for endoscopic urologic procedure involving mucosal trauma 3
• Patient has underlying urinary tract abnormalities 3

Treatment regimens for symptomatic non-pregnant patients:

• Penicillin G 500 mg orally every 6-8 hours for 7-10 days (preferred) 3
• Ampicillin 500 mg orally every 8 hours for 7-10 days (acceptable alternative) 3
• For severe infections requiring IV therapy: Ampicillin 2 g IV every 4-6 hours, then transition to oral therapy once clinically stable 2
• For complicated infections or when prostatitis cannot be excluded in men: extend treatment to 14 days 2

For penicillin-allergic patients:

• Clindamycin 300-450 mg orally every 8 hours (requires susceptibility testing) 3

When Treatment IS NOT Indicated

Do NOT treat asymptomatic GBS bacteriuria in non-pregnant patients, regardless of colony count. 3

This applies to:

• Adults with diabetes mellitus 3
• Elderly or institutionalized individuals 3
• Patients with indwelling urinary catheters (short-term or long-term) 3
• Individuals with neurogenic bladder on intermittent catheterization 3
• Patients undergoing non-urologic surgery (including orthopedic/arthroplasty) 3
• Patients with history of recurrent UTIs 3

Rationale: Treating asymptomatic bacteriuria leads to unnecessary antibiotic exposure, increased resistance, and adverse drug effects without clinical benefit 3

---

Antibiotic Susceptibility Data

• 100% susceptibility to penicillin, ampicillin, and vancomycin 5, 7, 8
• 13-25% resistance to clindamycin (requires susceptibility testing before use) 4, 5, 6
• 25-30% resistance to erythromycin 5, 6
• High susceptibility (>95%) to cephalothin, augmentin, lincomycin, chloramphenicol 7

---

Key Clinical Pitfalls

• Never use oral or IV antibiotics before labor to treat asymptomatic GBS vaginal colonization in pregnancy—this is completely ineffective at eliminating carriage and promotes antibiotic resistance 1
• Never use nitrofurantoin, fluoroquinolones, sulfonamides, or tetracyclines for GBS infections—they lack proven efficacy 2
• Always perform susceptibility testing before using clindamycin due to 13-25% resistance rates 4, 5, 6
• Underdosing or premature discontinuation leads to treatment failure and recurrence 2
• In non-pregnant patients with normal urinalysis and no symptoms, GBS in urine represents asymptomatic bacteriuria that should not be treated 3