What is the best oral antibiotic for an uncomplicated pansensitive Enterococcus faecalis (E. faecalis) urinary tract infection (UTI)?

Best Oral Antibiotic for Uncomplicated Pansensitive Enterococcus faecalis UTI

Ampicillin 500 mg orally every 8 hours is the best oral antibiotic for uncomplicated pansensitive Enterococcus faecalis UTI. 1

First-Line Treatment Options

• Ampicillin/Amoxicillin: Ampicillin 500 mg orally every 8 hours or amoxicillin 500 mg orally every 8 hours is recommended as first-line therapy for uncomplicated E. faecalis UTIs that are pansensitive 1
• Nitrofurantoin: 100 mg orally every 6 hours is an effective alternative with good in vitro activity against E. faecalis and low resistance rates 1, 2
• Fosfomycin: A single 3 g oral dose is FDA-approved specifically for E. faecalis UTIs and provides convenient single-dose therapy 1

Treatment Algorithm

1. Confirm susceptibility testing: Even though the strain is described as "pansensitive," verify susceptibility to guide therapy 1
2. Choose based on patient factors:
   • For patients without contraindications: Ampicillin/amoxicillin (first choice)
   • For patients with penicillin allergy: Nitrofurantoin or fosfomycin 1, 3
   • For patients preferring single-dose therapy: Fosfomycin 1

Evidence Strength and Considerations

• The recommendation for ampicillin/amoxicillin is supported by guidelines that recognize it as the drug of choice for enterococcal infections, including uncomplicated UTIs 1
• Clinical outcomes with ampicillin for E. faecalis UTIs show high rates of clinical (88.1%) and microbiological (86%) eradication 1
• Nitrofurantoin has demonstrated excellent activity against E. faecalis with studies showing 100% susceptibility in some series 2
• Fosfomycin has FDA approval specifically for E. faecalis UTIs and offers the convenience of single-dose therapy 1

Important Caveats

• Avoid fluoroquinolones: Despite historical use, ciprofloxacin is no longer recommended for E. faecalis UTIs due to increasing resistance rates (47-46% for ciprofloxacin/levofloxacin) and FDA warnings about unfavorable risk-benefit ratios for uncomplicated UTIs 1, 4
• Duration of therapy: 7 days is typically recommended for ampicillin/amoxicillin, 7 days for nitrofurantoin, and single dose for fosfomycin 1
• Monitor for recurrence: E. faecalis has been associated with persistent and recurrent UTIs even after appropriate therapy 5
• Catheter removal: If a urinary catheter is present, removal should be considered as part of management 3

Special Situations

• For patients with recurrent E. faecalis UTIs, antibiotic prophylaxis with nitrofurantoin may paradoxically increase virulence properties of enterococci and should be used with caution 5
• For complicated infections or pyelonephritis, parenteral therapy may be necessary with ampicillin or combination therapy 3