Treatment of Complicated UTI Caused by Enterococcus Species
For complicated UTI caused by Enterococcus species, ampicillin is the first-line treatment of choice based on the antibiotic sensitivity results showing susceptibility to this agent. 1
Antibiotic Selection Algorithm
First-line options (based on susceptibility testing):
- Ampicillin - Use when susceptible (as in this case)
- Nitrofurantoin - Effective for Enterococcus and shown to be susceptible in this case
Alternative options (if first-line cannot be used):
- High-dose gentamicin - Can be used in combination therapy for synergistic effect, but note this isolate shows high-level gentamicin susceptibility
- Vancomycin - Reserved for ampicillin-resistant strains or patients with β-lactam allergies
Treatment Regimen Details
For Ampicillin (Recommended):
- Dosage: 1-2g IV every 4-6 hours (adjust based on renal function)
- Duration: 7-14 days depending on clinical response
- Monitoring: Clinical improvement should occur within 48-72 hours
For Nitrofurantoin (Alternative):
- Dosage: 100mg orally twice daily
- Duration: 7-10 days for complicated UTI
- Contraindications: Avoid in patients with CrCl <60 mL/min, pregnancy at term, or G6PD deficiency 1
Special Considerations
- Catheter management: If a urinary catheter is present, it should be removed or replaced to improve treatment outcomes
- Resistance concerns: Enterococcus species are intrinsically resistant to cephalosporins (as confirmed by this isolate's resistance to cefazolin, cefepime, cefuroxime, and cefixime) 2
- Biofilm formation: Enterococci commonly form biofilms on catheters, which may require longer treatment duration
- Combination therapy: For severe infections, some evidence supports combination therapy with ampicillin plus ceftriaxone for synergistic effect, though this is more established for endocarditis than UTI 3
Follow-up Recommendations
- Obtain follow-up urine cultures 1-2 weeks after completing therapy if symptoms persist 1
- Evaluate for anatomical abnormalities or foreign bodies if recurrent infections occur
- Consider urological consultation for patients with recurrent complicated UTIs
Pitfalls to Avoid
- Do not use cephalosporins: Enterococci have intrinsic resistance to most cephalosporins, as confirmed by the sensitivity results
- Avoid fluoroquinolones as empiric therapy: High rates of resistance (up to 47% for ciprofloxacin) have been reported in Enterococcus faecalis 4
- Do not treat asymptomatic bacteriuria: Routine therapy for asymptomatic bacteriuria with Enterococcus is not recommended 5
- Avoid unnecessary prolonged courses: Extended treatment beyond 14 days rarely provides additional benefit and increases resistance risk 1
The antibiotic sensitivity profile in this case clearly guides therapy toward ampicillin as the most appropriate choice, with nitrofurantoin as a reasonable oral alternative for step-down therapy if the patient shows clinical improvement.