What antibiotic is recommended for a patient with a urinary tract infection (UTI) caused by Escherichia coli?

Antibiotic Treatment for E. coli Urinary Tract Infection

Nitrofurantoin 100 mg orally twice daily for 5 days is the recommended first-line antibiotic for this uncomplicated urinary tract infection caused by E. coli. 1, 2

First-Line Treatment Options

For uncomplicated UTI caused by E. coli, the following first-line options are recommended:

1. Nitrofurantoin 100 mg orally twice daily for 5 days

   • Excellent efficacy against E. coli with very low resistance rates (0.9%) 2
   • High susceptibility rate of 95.6% for E. coli isolates 3
   • Recommended by clinical guidelines as a first-line treatment 1

2. Fosfomycin 3 g orally as a single dose

   • Convenient single-dose regimen
   • Low resistance rates (4.3%) against E. coli 2
   • Recommended by guidelines for uncomplicated UTIs 1

3. Trimethoprim-sulfamethoxazole 160/800 mg orally twice daily for 3 days

   • Consider only if local resistance patterns show <20% resistance 1
   • Higher resistance rates (20-29%) limit empiric use in many regions 3, 2

Treatment Algorithm

1. For uncomplicated UTI with E. coli:

   • Start with nitrofurantoin 100 mg orally twice daily for 5 days
   • Alternative: fosfomycin 3 g single oral dose

2. If patient has contraindications to nitrofurantoin (CrCl <30 mL/min, pregnancy near term, or signs of pyelonephritis):

   • Use fosfomycin 3 g as a single oral dose

3. If patient has contraindications to both nitrofurantoin and fosfomycin:

   • Consider trimethoprim-sulfamethoxazole if local resistance patterns permit

4. For complicated UTI or treatment failure:

   • Consider extending treatment duration to 7-10 days
   • Consider alternative agents based on susceptibility testing

Important Considerations

• Avoid fluoroquinolones (e.g., ciprofloxacin) for uncomplicated UTIs despite FDA approval for E. coli UTIs 4 due to:

  • High resistance rates (24-49.9%) 3, 2
  • Unfavorable risk-benefit ratio 1
  • Need to preserve for more invasive infections 5

• Avoid beta-lactams as first-line therapy as they are less effective for empirical treatment of uncomplicated UTIs 5

• Monitor for clinical improvement within 48-72 hours of starting treatment 1

• No need for follow-up urine culture if symptoms resolve 1

Special Situations

• If signs of pyelonephritis develop (fever, flank pain, systemic symptoms):

  • Switch to broader coverage and longer duration (10-14 days)
  • Consider hospitalization if severe

• For persistent or recurrent symptoms:

  • Obtain urine culture with susceptibility testing
  • Evaluate for structural abnormalities or other underlying conditions
  • Consider extended treatment duration (7-10 days) 1

Nitrofurantoin is the optimal choice for this patient with an uncomplicated E. coli UTI due to its high efficacy, low resistance rates, and favorable safety profile compared to alternatives.