Does macrobid (nitrofurantoin) cover Group B Streptococcus (Streptococcus agalactiae) in a urinary tract infection?

Does Nitrofurantoin (Macrobid) Cover Group B Streptococcus for UTI?

Yes, nitrofurantoin has good in vitro activity against Group B Streptococcus (Streptococcus agalactiae) and is an appropriate treatment option for uncomplicated lower urinary tract infections caused by this organism. 1, 2

Evidence Supporting Nitrofurantoin for GBS UTI

Microbiologic Activity

• Nitrofurantoin demonstrates broad-spectrum bactericidal activity against both Gram-positive and Gram-negative uropathogens, including Enterococcus species and other streptococcal organisms 2
• Clinical studies confirm nitrofurantoin's effectiveness against Streptococcus faecalis (another streptococcal species), with documented cure rates of 85-94% in urinary tract infections 3
• The drug interferes with bacterial cell wall synthesis, protein production, and DNA replication in both Gram-positive and Gram-negative pathogens 2

Guideline Support for Streptococcal UTIs

• International guidelines specifically recommend nitrofurantoin (100 mg PO every 6 hours) for uncomplicated urinary tract infections caused by vancomycin-resistant Enterococcus, demonstrating its efficacy against resistant Gram-positive cocci 1
• Nitrofurantoin is positioned as a first-line agent for uncomplicated cystitis with minimal resistance patterns and low collateral damage to normal flora 4, 5

Recommended Dosing for GBS Cystitis

Standard regimen: Nitrofurantoin 100 mg orally twice daily for 5-7 days 4, 3

• The 5-day course is typically sufficient for uncomplicated cystitis 4
• A 7-day course may be considered for persistent symptoms or in patients with complicating factors 3

Important Clinical Considerations

When to Obtain Cultures

• Urine culture is NOT routinely needed for typical uncomplicated cystitis presentations 4
• Obtain urine culture when: suspected pyelonephritis, symptoms persist or recur within 4 weeks after treatment, atypical symptoms, pregnancy, male gender, or elderly patients (≥65 years) 4

Contraindications and Limitations

• Contraindicated in: last trimester of pregnancy, any degree of renal impairment (CrCl <60 mL/min), and suspected pyelonephritis 6, 5
• Nitrofurantoin achieves high urinary concentrations but inadequate tissue penetration, making it unsuitable for upper tract infections or systemic GBS infections 5

Special Warning for GBS

• Group B Streptococcus can cause invasive infections beyond simple cystitis, including pyelonephritis, urosepsis, and rarely secondary abscesses 7
• If the patient presents with fever, flank pain, severe abdominal/pelvic pain, or systemic symptoms, do NOT use nitrofurantoin 7, 5
• These presentations require parenteral therapy with agents that achieve adequate tissue penetration (e.g., ampicillin, ceftriaxone, or fluoroquinolones) 1, 4

Common Pitfalls to Avoid

• Do not use nitrofurantoin for complicated UTIs or pyelonephritis, even if the organism is GBS—inadequate tissue levels will lead to treatment failure 5
• Do not treat asymptomatic bacteriuria (except in pregnancy or before urologic procedures), as this increases antimicrobial resistance without clinical benefit 4
• Do not prescribe for elderly patients with reduced renal function, as this increases risk of serious adverse effects including pulmonary reactions and polyneuropathy 6, 5

Alternative Agents if Nitrofurantoin is Contraindicated

For GBS cystitis when nitrofurantoin cannot be used:

• Ampicillin 500 mg orally every 8 hours remains highly effective against GBS 1
• Fosfomycin 3 g single dose may be considered, though data specific to GBS are limited 4
• Trimethoprim-sulfamethoxazole should be avoided unless susceptibility is confirmed, as resistance patterns vary 4