Is ertapenem appropriate for treating an Enterococcus faecalis urinary tract infection?

Ertapenem is NOT Appropriate for Enterococcus faecalis UTI

Ertapenem lacks activity against all Enterococcus species, including E. faecalis, and should never be used for this infection regardless of reported susceptibility. 1

Why Ertapenem Cannot Be Used

• Ertapenem has an inherent spectrum gap that excludes all Enterococcus species, unlike other carbapenems (imipenem, meropenem, doripenem) which retain some enterococcal activity 1
• The reported "sensitivity" on your culture is likely a laboratory error or misinterpretation, as enterococci possess intrinsic resistance to ertapenem through structural differences in penicillin-binding proteins 1
• All cephalosporins and ertapenem have natural resistance patterns against E. faecalis and should be avoided 2

Correct Treatment Options for E. faecalis UTI

First-Line Therapy (Uncomplicated UTI)

• Ampicillin/amoxicillin remains the drug of choice, with high-dose ampicillin (18-30 g IV daily in divided doses) or amoxicillin 500 mg IV/PO every 8 hours for 7 days achieving 88.1% clinical cure and 86% microbiological eradication rates 2, 3
• High urinary concentrations of ampicillin can overcome elevated MICs even in ampicillin-resistant strains, making it effective when in vitro testing suggests resistance 2

Alternative Oral Agents

• Fosfomycin 3 g orally as a single dose is FDA-approved specifically for E. faecalis UTI and recommended for uncomplicated infections 2, 3
• Nitrofurantoin 100 mg orally every 6 hours for 7 days has good in vitro activity with resistance rates below 6% in E. faecalis 2, 3
• Nitrofurantoin should NOT be used if creatinine clearance <60 mL/min or for complicated UTI/pyelonephritis due to poor tissue penetration 2

For Vancomycin-Resistant E. faecalis (VRE)

• Linezolid 600 mg IV/PO every 12 hours is recommended for enterococcal infections, with treatment duration dependent on site and clinical response 4
• High-dose daptomycin 8-12 mg/kg/day IV may be used for severe VRE UTIs with bacteremia 2

Critical Clinical Pitfalls

• Always differentiate colonization from true infection before prescribing anti-enterococcal agents, as asymptomatic bacteriuria does not require treatment 2, 3
• Fluoroquinolones should be avoided due to high resistance rates (46-47% for ciprofloxacin/levofloxacin in E. faecalis) 2, 5
• Empiric enterococcal coverage is not necessary for community-acquired intra-abdominal infections 4
• Obtain susceptibility testing before initiating therapy, even for strains described as "pansensitive" 2

Treatment Duration

• 7 days for uncomplicated cystitis achieves optimal eradication rates 2, 3
• 10-14 days if complicating factors present including upper tract involvement, systemic symptoms, or urinary retention 2