What is the recommended treatment for a non-pregnant patient with a mild to moderate Group B strep (GBS) urinary tract infection (UTI) who is being considered for Macrobid (nitrofurantoin)?

Treatment of Group B Streptococcus UTI with Macrobid (Nitrofurantoin)

Nitrofurantoin is an appropriate and effective treatment option for uncomplicated Group B Streptococcus urinary tract infections in non-pregnant adults, as it demonstrates good in vitro activity against GBS and achieves therapeutic urinary concentrations. 1, 2

First-Line Treatment Recommendations

For non-pregnant patients with mild to moderate GBS UTI, you have two equally effective first-line options:

• Ampicillin 500 mg orally every 8 hours for 3-7 days is the traditional first-line treatment 3
• Amoxicillin 500 mg orally every 8 hours for 3-7 days is an acceptable alternative with similar efficacy 3
• Nitrofurantoin (Macrobid) is a valid alternative that achieves urinary concentrations 25- to 100-fold above therapeutic levels, making it particularly effective for lower UTIs 1

Why Nitrofurantoin Works for GBS UTI

• All GBS clinical isolates tested in susceptibility studies showed sensitivity to nitrofurantoin, with only 2% exhibiting intermediate sensitivity 2
• Nitrofurantoin has the advantage of minimal selective pressure on vaginal microflora compared to broader-spectrum agents 2
• The high urinary concentrations achieved make it especially suitable for lower urinary tract infections caused by GBS 1

Treatment Duration

• Uncomplicated UTI: 3-7 days of therapy 3
• Complicated UTI: 5-7 days of therapy 3
• Obtain urine culture before initiating therapy to confirm diagnosis and guide treatment 3

Critical Pregnancy Exclusion

If your patient is pregnant or could be pregnant, DO NOT use nitrofurantoin for GBS bacteriuria:

• GBS bacteriuria detected during pregnancy at any concentration requires documentation for intrapartum antibiotic prophylaxis planning, not immediate treatment 1, 4
• Pregnant women with GBS bacteriuria should receive intravenous penicillin G (5 million units IV initial dose, then 2.5 million units IV every 4 hours) or ampicillin (2 g IV initial dose, then 1 g IV every 4 hours) during labor, not prenatal oral antibiotics 1
• Oral antimicrobial agents should not be used to treat asymptomatic GBS colonization during pregnancy, as this is ineffective in preventing neonatal disease 5, 1

Penicillin Allergy Alternatives

For non-pregnant patients with penicillin allergies:

• Non-severe allergy: Cefazolin 2 g IV initial dose, then 1 g IV every 8 hours (for severe infections requiring IV therapy) 3
• Severe allergy with confirmed susceptibility: Clindamycin 300-450 mg orally every 6 hours, but only if antimicrobial susceptibility testing confirms GBS susceptibility (19% of isolates show resistance) 3, 2
• Vancomycin may be considered for severe infections with significant beta-lactam allergies 3

Common Pitfalls to Avoid

• Do not confuse colonization with infection: Significant bacteriuria is defined as ≥50,000 CFUs/mL of a single urinary pathogen 3
• Do not use nitrofurantoin in pregnancy for GBS bacteriuria: This is a documentation issue for intrapartum prophylaxis, not a treatment indication 1, 4
• Do not assume all antibiotics work: 31% of GBS isolates showed resistance to azithromycin and ceftriaxone, 19% to clindamycin, and 15% to cefazolin in susceptibility testing 2
• Verify susceptibility in penicillin-allergic patients: 35% of clinical isolates were resistant to 6 of 12 antibiotics tested, making susceptibility testing crucial when selecting alternatives 2

Monitoring and Follow-Up

• Consider follow-up urine culture after treatment completion to ensure eradication, especially in complicated cases 3
• For complicated or recurrent infections, evaluate for structural urinary tract abnormalities 3