What is the recommended treatment for a urinary tract infection caused by Enterococcus faecalis?

Treatment for Enterococcus faecalis Urinary Tract Infection

For uncomplicated E. faecalis UTI, start with amoxicillin 500 mg orally every 8 hours for 7 days, which achieves 88.1% clinical cure and 86% microbiological eradication rates. 1, 2, 3

First-Line Treatment Algorithm

For outpatient oral therapy:

• Amoxicillin 500 mg PO every 8 hours for 7 days is the American College of Physicians' first-line recommendation 1, 2, 3
• Ampicillin 500 mg PO every 8 hours for 7 days is an equivalent alternative with identical efficacy 1, 2, 3

For hospitalized patients requiring IV therapy:

• Ampicillin 2 g IV every 4 hours (or high-dose 18-30 g daily in divided doses) to achieve sufficient urinary concentrations 1, 2, 3
• The high urinary concentrations can overcome high ampicillin MICs even in ampicillin-resistant VRE strains, making it effective despite in vitro resistance 1, 3

Alternative Treatment Options

Single-dose therapy:

• Fosfomycin 3 g as a single oral dose is FDA-approved specifically for E. faecalis UTIs and offers convenient single-dose therapy for uncomplicated infections 1, 2, 3, 4
• This is particularly useful for uncomplicated acute cystitis in women 4

Multi-day alternative:

• Nitrofurantoin 100 mg PO every 6 hours for 7 days has excellent activity with resistance rates below 6% 1, 2, 3

Critical Pre-Treatment Steps

Always obtain urine culture and susceptibility testing before initiating therapy, even for strains described as "pansensitive," because resistance patterns vary significantly by institution and patient population. 1, 2, 3

Differentiate true infection from asymptomatic bacteriuria:

• Colonization with E. faecalis does not routinely require treatment 1, 3
• Only treat symptomatic UTIs with pyuria and clinical signs of infection 1, 3

Special Clinical Situations

For vancomycin-resistant E. faecalis (VRE):

• Fosfomycin 3 g single dose for uncomplicated UTI 2, 3
• Nitrofurantoin 100 mg PO every 6 hours for uncomplicated UTI 2, 3
• High-dose ampicillin can still be effective due to high urinary concentrations overcoming resistance 1, 3

For penicillin allergy:

• Nitrofurantoin 100 mg PO every 6 hours for 7 days 1, 3

For beta-lactamase producing strains:

• Replace amoxicillin with amoxicillin-clavulanate 500 mg PO every 8 hours for 7 days 1, 3

For complicated UTI or pyelonephritis:

• Longer treatment durations are necessary, though specific evidence for E. faecalis is limited 1, 2, 3
• Fosfomycin is NOT indicated for pyelonephritis or perinephric abscess per FDA labeling 4

What to Avoid

Fluoroquinolones should be avoided due to:

• High resistance rates of 46-47% for ciprofloxacin/levofloxacin 1, 2, 3
• Unfavorable risk-benefit profile for uncomplicated UTIs 2, 3

Common Pitfalls

Do not assume susceptibility without testing:

• Even "pansensitive" strains require confirmation as institutional resistance patterns vary 1, 2, 3

Do not treat asymptomatic bacteriuria:

• E. faecalis colonization is common and does not require antibiotics unless symptomatic 1, 3

Do not use fosfomycin for upper tract infections:

• FDA approval is limited to uncomplicated cystitis only 4
• If bacteriuria persists or reappears after fosfomycin, select alternative agents 4

Do not underdose ampicillin for serious infections:

• High-dose regimens (18-30 g daily IV) are needed to achieve therapeutic urinary concentrations 1