Macrobid (Nitrofurantoin) for Group B Streptococcus Treatment
Macrobid (nitrofurantoin) is NOT recommended for treating Group B streptococcus (GBS) infections, as penicillin or ampicillin remain the definitive first-line treatments with 100% susceptibility and no documented resistance worldwide. 1, 2
Why Nitrofurantoin Should Not Be Used
- GBS remains universally susceptible to penicillin, with no resistance documented over decades of use, making penicillin-based antibiotics the clear choice. 2, 3
- Nitrofurantoin is not mentioned in any major guidelines for GBS treatment, including those from the Centers for Disease Control and Prevention, American College of Obstetricians and Gynecologists, or Infectious Diseases Society of America. 1, 4
- The narrow spectrum and proven efficacy of penicillin make it superior to broader-spectrum agents that promote antibiotic resistance. 5
Correct First-Line Treatment Options
For GBS Urinary Tract Infections (Non-Pregnant)
- Ampicillin 500 mg orally every 8 hours for 3-7 days is the recommended first-line treatment for uncomplicated GBS UTIs in adults. 4
- Amoxicillin 500 mg orally every 8 hours can be used as an alternative with similar efficacy. 4
- For complicated UTIs or severe infections, higher doses of ampicillin (up to 18-30 g/day IV in divided doses) may be required. 4
For GBS Urinary Tract Infections (Pregnant)
- Any concentration of GBS in urine during pregnancy requires intrapartum antibiotic prophylaxis during labor, regardless of colony count, due to increased risk of early-onset neonatal disease. 1
- Penicillin G is the preferred first-line treatment, with ampicillin as an acceptable alternative, at a dosage of 500 mg orally every 6-8 hours for 7-10 days. 1
- For intrapartum prophylaxis: penicillin G 5 million units IV initially, then 2.5 million units IV every 4 hours until delivery, which is 78% effective in preventing early-onset GBS disease. 1
Penicillin-Allergic Patients
Non-Severe Allergy (No Anaphylaxis History)
- Cefazolin 2 g IV initial dose, then 1 g IV every 8 hours is recommended for patients without history of anaphylaxis, angioedema, or respiratory distress. 1, 4
Severe Allergy (High Risk for Anaphylaxis)
- Clindamycin 900 mg IV every 8 hours or 300-450 mg orally every 6 hours may be used ONLY if susceptibility testing confirms the GBS isolate is sensitive. 1, 4, 2
- Susceptibility testing is mandatory before using clindamycin, as approximately 20% of GBS isolates are resistant, and empirical use is not recommended. 1, 2
- Vancomycin 1 g IV every 12 hours is the preferred alternative when susceptibility testing is unavailable or resistance is confirmed. 2
Critical Pitfalls to Avoid
- Never use nitrofurantoin, fluoroquinolones, sulfonamides, or tetracyclines for GBS infections, as they lack proven efficacy and are not recommended in any guidelines. 5
- Underdosing or premature discontinuation of antibiotic treatment leads to treatment failure and recurrence. 1
- Using clindamycin without susceptibility testing risks treatment failure due to varying resistance rates (ranging from 20-45% in different regions). 1, 3, 6
- In pregnant women, failing to provide intrapartum prophylaxis for any GBS bacteriuria increases neonatal mortality risk. 1