What is the oral (p.o.) antibiotic treatment for Streptococcus B (Strep B) in urine?

Oral Antibiotic Treatment for Group B Streptococcus in Urine

For Group B Streptococcus (GBS) in urine, amoxicillin 500 mg orally three times daily for 10 days is the recommended first-line treatment.

First-Line Treatment Options

Amoxicillin

• Dosage: 500 mg orally three times daily for 10 days
• Evidence: Amoxicillin has excellent activity against GBS, which remains universally susceptible to beta-lactam antibiotics 1
• Advantages: Well-tolerated, inexpensive, and highly effective against GBS

Alternative Dosing for Amoxicillin

• Once-daily dosing: 750 mg once daily for 10 days may be considered for improved compliance 2
• Twice-daily dosing: 500 mg twice daily for 10 days is also effective and may improve adherence 3

Alternative Options for Penicillin-Allergic Patients

Non-Anaphylactic Penicillin Allergy

• First-generation cephalosporins (e.g., cephalexin 500 mg orally four times daily for 10 days) 4

Severe Penicillin Allergy (Anaphylaxis)

• Clindamycin: 300-450 mg orally three times daily for 10 days 4
• Trimethoprim-sulfamethoxazole (TMP-SMX): 1-2 double-strength tablets twice daily for 10 days 4, 5
  • Note: Confirm susceptibility before using TMP-SMX as resistance patterns may vary

Special Considerations

Uncomplicated Urinary Tract Infections

• For uncomplicated UTIs due to GBS, a single dose of fosfomycin 3 g orally may be considered, though evidence is limited 4
• Nitrofurantoin 100 mg orally every 6 hours is another alternative for uncomplicated UTIs 4

Complicated Infections

• For patients with systemic symptoms, pyelonephritis, or other complicating factors:
  • Consider initial IV therapy followed by oral step-down therapy
  • Extend treatment duration to 14 days

Monitoring and Follow-Up

• Clinical improvement should be evident within 48-72 hours of starting appropriate therapy
• Consider follow-up urine culture 1-2 weeks after completing therapy in:
  • Pregnant patients
  • Patients with recurrent UTIs
  • Patients with structural abnormalities of the urinary tract

Common Pitfalls to Avoid

1. Inadequate duration of therapy: Complete the full 10-day course even if symptoms resolve earlier
2. Inappropriate antibiotic selection: Avoid macrolides as empiric therapy for penicillin-allergic patients due to increasing resistance rates (up to 18% for erythromycin) 1
3. Failure to recognize complicated infections: Assess for signs of systemic illness, pyelonephritis, or underlying urologic abnormalities
4. Overlooking pregnancy status: GBS in urine during pregnancy requires special management protocols not covered in this response

Treatment Algorithm

1. First-line: Amoxicillin 500 mg PO TID for 10 days
2. If compliance is a concern: Consider amoxicillin 750 mg PO once daily for 10 days
3. For non-anaphylactic penicillin allergy: Cephalexin 500 mg PO QID for 10 days
4. For severe penicillin allergy: Clindamycin 300-450 mg PO TID for 10 days
5. For uncomplicated UTI with penicillin allergy: Consider fosfomycin 3 g single dose or nitrofurantoin 100 mg PO QID

Remember that GBS remains universally susceptible to beta-lactam antibiotics, making amoxicillin the optimal first-line oral therapy for this infection.