Can a patient with Enterococcus faecalis use Macrobid (nitrofurantoin) as a treatment option?

Macrobid (Nitrofurantoin) for Enterococcus faecalis

Nitrofurantoin is an appropriate treatment option for uncomplicated urinary tract infections caused by Enterococcus faecalis, with resistance rates below 6% and demonstrated clinical efficacy. 1

When Nitrofurantoin Should Be Used

For uncomplicated UTIs caused by E. faecalis:

• Nitrofurantoin 100 mg orally every 6 hours for 7 days is recommended as an effective alternative to ampicillin/amoxicillin 1
• This agent maintains excellent in vitro activity against E. faecalis with consistently low resistance rates 1, 2
• It serves as the preferred alternative for patients with penicillin allergies 1

Critical Limitations of Nitrofurantoin

Nitrofurantoin should NOT be used for:

• Complicated urinary tract infections or pyelonephritis, as it achieves poor tissue and serum concentrations 1
• Systemic enterococcal infections (bacteremia, endocarditis, intra-abdominal infections), where ampicillin-based regimens remain the standard of care 3
• Patients with creatinine clearance <60 mL/min, as urinary concentrations become inadequate

First-Line Treatment Hierarchy for E. faecalis UTI

The treatment algorithm should follow this priority:

1. First-line: Amoxicillin 500 mg orally every 8 hours for 7 days (88.1% clinical success rate) 1
2. Alternative: Nitrofurantoin 100 mg orally every 6 hours for 7 days 1
3. Single-dose option: Fosfomycin 3 g orally as a single dose (FDA-approved specifically for E. faecalis UTI) 1, 4

Essential Clinical Considerations

Always obtain susceptibility testing before initiating therapy, even for strains described as "pansensitive," as resistance patterns vary significantly by institution 1

Differentiate colonization from true infection before prescribing antibiotics, as asymptomatic bacteriuria with E. faecalis does not routinely require treatment 1, 4

Avoid fluoroquinolones due to high resistance rates (46-47% for ciprofloxacin/levofloxacin) and unfavorable risk-benefit ratios for uncomplicated UTIs 1

For Invasive E. faecalis Infections

For serious infections (endocarditis, bacteremia, intra-abdominal infections):

• Ampicillin remains the drug of choice, with high-dose regimens (18-30 g IV daily in divided doses) recommended 3, 1
• Combination therapy with gentamicin (if not high-level resistant) or alternative dual beta-lactam therapy should be considered for endocarditis 3
• Piperacillin-tazobactam and vancomycin are acceptable alternatives based on susceptibility testing 3