What is the recommended treatment for a urinary tract infection (UTI) with a urine culture showing significant growth of Enterococcus faecalis at a colony count of 50,000-60,000 colony-forming units per milliliter (CFU/mL)?

Treatment of Enterococcus faecalis UTI with Colony Count 50,000-60,000 CFU/mL

Ampicillin/amoxicillin is the drug of choice for this Enterococcus faecalis urinary tract infection, with oral amoxicillin 500 mg every 8 hours for 7 days as first-line therapy for uncomplicated cases, regardless of whether the colony count is slightly below the traditional 100,000 CFU/mL threshold. 1

Colony Count Interpretation

• The colony count of 50,000-60,000 CFU/mL falls below the traditional threshold of >100,000 CFU/mL typically cited for UTI diagnosis 2
• However, this does not automatically exclude true infection—clinical symptoms must guide treatment decisions, as asymptomatic bacteriuria should not be treated 3
• If the patient has UTI symptoms (dysuria, frequency, urgency, suprapubic pain), treat as a true infection despite the lower colony count 3
• If the patient is asymptomatic, this represents colonization and treatment should be avoided to prevent antimicrobial resistance 3

First-Line Treatment for Symptomatic Infection

Oral therapy options (in order of preference):

• Amoxicillin 500 mg orally every 8 hours for 7 days achieves 88.1% clinical and 86% microbiological eradication rates 1
• Ampicillin 500 mg orally every 8 hours for 7 days is an equivalent alternative 1
• High urinary concentrations of ampicillin/amoxicillin can overcome elevated MICs even in ampicillin-resistant strains, making these agents effective despite in vitro resistance 2, 1

Alternative Oral Agents

If penicillin allergy or intolerance:

• Nitrofurantoin 100 mg orally every 6 hours for 7 days has excellent activity against E. faecalis with resistance rates below 6% 1, 4
• Fosfomycin 3 g orally as a single dose is FDA-approved specifically for E. faecalis UTI and recommended for uncomplicated infections 1, 5

Critical Treatment Considerations

Obtain susceptibility testing before initiating therapy:

• Even for strains described as "pansensitive," resistance patterns vary significantly by institution 1
• This is essential to guide definitive therapy and avoid treatment failure 2

Avoid fluoroquinolones:

• Ciprofloxacin and levofloxacin resistance rates reach 46-47% in E. faecalis 1, 6
• Clinical outcomes with fluoroquinolones are poor for enterococcal infections despite reported susceptibility 3, 6
• Hospital-acquired infections and prior healthcare exposure significantly increase fluoroquinolone resistance risk 6

Catheter-Associated Considerations

If the patient has an indwelling urinary catheter:

• Remove the catheter if clinically feasible, as catheter retention is associated with treatment failure 3
• If the catheter must remain, use the same antibiotic regimen (ampicillin/amoxicillin) for 7-14 days 3
• Consider antibiotic lock therapy in addition to systemic therapy for persistent catheter-associated infection 3
• Monitor for signs of complicated infection including fever, rigors, or persistent bacteremia that would warrant evaluation for endocarditis 3

Parenteral Therapy Indications

Switch to IV therapy if:

• The patient cannot tolerate oral medications
• There are signs of pyelonephritis or complicated UTI
• High-dose ampicillin 18-30 g IV daily in divided doses or amoxicillin 500 mg IV every 8 hours is recommended for hospitalized patients 1

Common Pitfalls to Avoid

• Do not treat asymptomatic bacteriuria—this is extremely common and treatment fosters antimicrobial resistance without clinical benefit 3
• Do not dismiss the infection based solely on colony count—symptomatic patients with 50,000-60,000 CFU/mL may have true infection requiring treatment 2
• Do not use cephalosporins—enterococci have intrinsic resistance to cephalosporins, and their use promotes enterococcal colonization 7
• Do not use empiric glycopeptides (vancomycin) for community-acquired E. faecalis—reserve these for vancomycin-resistant enterococci or severe nosocomial infections 7