Treatment of E. coli and Enterococcus faecalis UTI
For uncomplicated UTIs caused by E. coli or Enterococcus faecalis, use first-line oral therapy with nitrofurantoin, trimethoprim-sulfamethoxazole (TMP-SMX), or fosfomycin for 5-7 days, selecting the agent based on your local antibiogram and recent antibiotic exposure history. 1
First-Line Antibiotic Selection
The choice among first-line agents should follow this hierarchy:
- Nitrofurantoin is highly effective against both E. coli (>95% susceptibility) and Enterococcus faecalis, with minimal collateral damage to normal flora and low resistance rates even with recurrent infections 1, 2
- TMP-SMX remains effective if local resistance rates are <20% and the patient has not received it in the past 3 months 1, 3
- Fosfomycin (single 3-gram dose) demonstrates excellent activity against E. coli (96% susceptibility) and Enterococcus faecalis, making it particularly useful when other agents are contraindicated 1, 2
Avoid fluoroquinolones as first-line therapy due to the FDA's 2016 advisory warning against their use in uncomplicated UTIs, citing unfavorable risk-benefit ratios from serious adverse effects including tendon rupture and peripheral neuropathy 1, 4
Treatment Duration
- Treat for 5-7 days maximum for uncomplicated cystitis in women, as longer courses increase resistance without improving outcomes 1
- Extend to 7-14 days for UTIs in men, with 14 days recommended when prostatitis cannot be excluded 5
- Single-dose therapy is inferior to short-course treatment, showing increased bacteriological persistence (RR 2.01) 1
Special Considerations for Enterococcus faecalis
When Enterococcus faecalis is identified on culture:
- Ampicillin (8 mg/L) inhibits all E. faecalis isolates and is the preferred agent if susceptibility is confirmed 6
- Nitrofurantoin and fosfomycin are excellent oral alternatives for uncomplicated UTI caused by E. faecalis 7, 2
- Avoid cephalosporins entirely, as Enterococcus species have intrinsic resistance to all cephalosporins 7
Complicated UTI Management
For complicated UTIs (indwelling catheters, structural abnormalities, immunosuppression, or signs of systemic infection):
- Obtain urine culture before initiating antibiotics to guide definitive therapy 1, 5
- Start empirical broad-spectrum coverage targeting both Enterobacteriaceae and Enterococci if sepsis or systemic signs are present 1
- Consider parenteral therapy initially with ceftriaxone (1-2g IV daily) or amoxicillin-clavulanate plus aminoglycoside, then transition to oral therapy after 24-48 hours of clinical improvement 8
- Treat for 7-14 days total depending on clinical response and patient sex 8
Resistance Patterns to Monitor
- E. coli resistance to fluoroquinolones has increased dramatically, with some cohorts showing 84% persistent resistance to ciprofloxacin 1
- Ampicillin resistance in E. coli exceeds 80% in many regions, making it unsuitable for empirical therapy 1
- Nitrofurantoin maintains low resistance with only 2.6% prevalence at initial infection and 5.7% at 9 months 1
Critical Pitfalls to Avoid
- Do not treat asymptomatic bacteriuria in non-pregnant patients, as this increases resistance without clinical benefit 1
- Do not use beta-lactams as first-line therapy due to collateral damage effects and propensity to promote rapid UTI recurrence 1
- Do not prescribe fluoroquinolones for recurrent UTI or in patients with recent fluoroquinolone exposure, as resistance rates exceed 80% in these populations 1, 9
- Expect clinical improvement within 24-48 hours; if symptoms persist beyond 48-72 hours, obtain imaging to evaluate for complications such as abscess or obstruction 8