Recurrent E. coli UTI: Re-treatment with Nitrofurantoin
For a patient with recurrent E. coli UTI that remains susceptible to nitrofurantoin, re-treatment with nitrofurantoin is the optimal choice, as it maintains excellent efficacy (>95% susceptibility), minimizes resistance development, and should be used preferentially for uncomplicated lower UTI. 1
Rationale for Re-treatment with Nitrofurantoin
Why Nitrofurantoin Remains First-Line
Nitrofurantoin maintains exceptionally low resistance rates (0.9-2.3%) in E. coli compared to alternatives like fluoroquinolones (24% resistance) or trimethoprim-sulfamethoxazole (20-29% resistance). 1, 2, 3
Resistance to nitrofurantoin decays quickly when present, making it particularly suitable for re-treatment even in recurrent UTI cases. 1
Current guidelines explicitly recommend nitrofurantoin as a first-choice agent for lower UTI treatment, with dosing of 100 mg twice daily for 5 days. 1
Confirming Appropriate Use
Before re-treating, verify this is truly uncomplicated lower UTI (cystitis) by ensuring:
No fever or systemic symptoms - nitrofurantoin does NOT achieve adequate serum/tissue concentrations for pyelonephritis or upper tract infections. 4, 5
Normal renal function (creatinine clearance >60 mL/min) - nitrofurantoin is contraindicated in renal impairment. 5
No signs of complicated UTI - avoid misclassifying recurrent UTI as "complicated" unless structural/functional abnormalities or immunosuppression exist. 1
Urine pH <8 - alkaline urine predicts nitrofurantoin resistance. 4
Treatment Protocol
Acute Treatment
Obtain pre-treatment urine culture before initiating therapy to document susceptibility and guide future treatment if needed. 1
Prescribe nitrofurantoin monohydrate/macrocrystals 100 mg twice daily for 5 days (or macrocrystals 50-100 mg four times daily for 5 days). 1
Consider self-start therapy for reliable patients who can obtain urine specimens before starting antibiotics. 1
Post-Treatment Management
No routine post-treatment cultures are needed if symptoms resolve completely. 1
Repeat urine culture only if symptoms persist despite treatment or recur within 2-4 weeks. 1
If symptoms persist, assume resistance to the original agent and use a 7-day course of an alternative antibiotic based on culture results. 1
Prevention Strategy for Recurrent UTI
Since this patient has had multiple UTIs (≥2 in 6 months qualifies as recurrent UTI), implement prevention measures: 1
Non-Antibiotic Interventions First
Increase fluid intake - may reduce UTI recurrence risk. 1
Behavioral modifications including proper hygiene and post-coital voiding if infections are coitus-related. 1
Prophylaxis Options (if non-antibiotic measures fail)
For premenopausal women with post-coital infections:
- Low-dose antibiotic within 2 hours of sexual activity for 6-12 months. 1
For premenopausal women with non-coital infections:
- Daily antibiotic prophylaxis (nitrofurantoin preferred) reduces UTI rate to 0.4/year, more effective than non-antibiotic alternatives. 1
For postmenopausal women:
- Vaginal estrogen with or without lactobacillus-containing probiotics as first-line prevention. 1
Non-antibiotic alternatives for any group:
- Methenamine hippurate and/or lactobacillus-containing probiotics for patients desiring antibiotic-sparing options. 1
Critical Pitfalls to Avoid
Do NOT treat asymptomatic bacteriuria - this fosters antimicrobial resistance and increases recurrent UTI episodes. 1
Do NOT use nitrofurantoin for febrile UTI or suspected pyelonephritis - inadequate tissue penetration makes treatment failure likely. 4, 5
Do NOT perform extensive workup (cystoscopy, imaging) in women <40 years with recurrent UTI and no risk factors. 1
Monitor for serious adverse effects with long-term use (>6 months): pulmonary reactions, hepatotoxicity, peripheral neuropathy, and hemolytic anemia in G6PD deficiency. 5
Avoid antibiotics for other indications within 8 weeks post-treatment - significantly increases recurrence risk after UTI treatment. 1