What is the recommended treatment for a urinary tract infection with Enterococcus faecalis (E. faecalis) bacteriuria, with a colony-forming unit (CFU) count of 50,000-60,000 CFU/mL?

Treatment of Enterococcus faecalis Bacteriuria at 50,000-60,000 CFU/mL

For a urine culture growing 50,000-60,000 CFU/mL of Enterococcus faecalis, treatment should only be initiated if the patient has urinary symptoms or is pregnant; asymptomatic bacteriuria does not require treatment in non-pregnant patients. 1, 2

Clinical Context Assessment

First, determine if treatment is indicated:

• Symptomatic UTI (dysuria, frequency, urgency, fever): Treat with antibiotics 1
• Asymptomatic bacteriuria in pregnancy: Always treat, as untreated cases progress to pyelonephritis in 20-35% and increase preterm birth risk 3
• Asymptomatic bacteriuria in non-pregnant patients: Do NOT treat routinely, as this may be harmful 2
• Catheter-associated: Consider catheter removal first; routine treatment of asymptomatic bacteriuria with multidrug-resistant Enterococcus is not recommended 2

The colony count of 50,000-60,000 CFU/mL meets the threshold for significant bacteriuria (≥50,000 CFU/mL) in the context of symptoms 1.

First-Line Treatment for Symptomatic Infection

Ampicillin or amoxicillin is the drug of choice for E. faecalis when the organism is susceptible:

• Oral regimen: Amoxicillin 500 mg PO every 8 hours for 7 days 4, 3
• IV regimen (if hospitalized/unable to tolerate oral): High-dose ampicillin 18-30g IV daily in divided doses 1, 4
• Rationale: The American Heart Association recommends ampicillin as first-line for E. faecalis infections, and high urinary concentrations can overcome resistance even in some resistant strains 4, 3

Treatment duration: 7 days is appropriate for uncomplicated lower UTI 3

Alternative Options for Penicillin Allergy or Resistance

If penicillin allergy or ampicillin resistance:

• Nitrofurantoin 100 mg PO every 6 hours for 5-7 days is the preferred alternative, with excellent in vitro activity against E. faecalis and resistance rates below 6% 1, 4, 5

  • Critical caveat: Only use for uncomplicated lower UTI/cystitis; do NOT use for pyelonephritis or complicated UTIs due to inadequate tissue penetration 4
  • Contraindication: Avoid if creatinine clearance <30-50 mL/min 4

• Fosfomycin 3g PO single dose is FDA-approved specifically for E. faecalis UTI and recommended for uncomplicated infections 1, 4, 3

Important Clinical Pitfalls

Avoid fluoroquinolones: E. faecalis demonstrates high resistance rates to ciprofloxacin (46-47%) and levofloxacin, making fluoroquinolones unreliable first-line agents 3, 6. Risk factors for ciprofloxacin resistance include hospital-acquired infection, treatment in urology departments, and transfer from healthcare centers 6.

Differentiate E. faecalis from E. faecium: E. faecalis is generally more susceptible to ampicillin with only 3% multidrug-resistant strains, compared to up to 95% for E. faecium 4. E. faecium infections are associated with higher mortality (23% vs. 10.1%), longer hospital stays, and more severe disease 7.

Always obtain susceptibility testing before finalizing therapy, even for "pansensitive" strains, as resistance patterns vary significantly 3.

Special Populations

Pregnancy:

• Screen all pregnant women for asymptomatic bacteriuria early in pregnancy 3
• Treat with amoxicillin 500 mg PO every 8 hours for 7 days as first-line 3
• Alternative: Nitrofurantoin 100 mg PO every 6 hours for 7 days if penicillin allergy 3
• Avoid fluoroquinolones due to teratogenic concerns 3

Healthcare-associated infections:

• Consider vancomycin-resistant strains if patient has prior antibiotic exposure, particularly cephalosporins 1
• For vancomycin-resistant E. faecalis: Linezolid 600 mg IV/PO every 12 hours or daptomycin 8-12 mg/kg/day 1, 4