What is the recommended treatment for a patient with a urinary tract infection caused by Escherichia coli?

Treatment of Urinary Tract Infection Caused by Escherichia coli

For this patient with a urinary tract infection caused by Escherichia coli showing resistance to ciprofloxacin, levofloxacin, gentamicin, and trimethoprim/sulfa, nitrofurantoin is the recommended first-line treatment based on the susceptibility results.

Interpretation of Laboratory Results

• The urinalysis shows signs of infection with positive leukocyte esterase (1+), elevated WBCs (10-20/HPF), and bacteria (few) 1
• The urine culture confirms moderate growth (10,000-49,000 CFU/mL) of Escherichia coli, which is the most common causative organism in urinary tract infections (75-80% of cases) 1
• The susceptibility testing reveals resistance to:
  • Ciprofloxacin (R)
  • Levofloxacin (R)
  • Gentamicin (R)
  • Trimethoprim/sulfamethoxazole (R) 1

Treatment Recommendations Based on Susceptibility

First-line options (based on susceptibility results):

• Nitrofurantoin - Susceptible (S, ≤16) and recommended for uncomplicated UTIs 1

  • Dosage: 100 mg twice daily for 5 days 1
  • Advantages: Low resistance rates (1.1% in North America) 2

• Amoxicillin/clavulanate - Susceptible (S, 4) 1, 3

  • Can be used for uncomplicated UTIs when first-line agents cannot be used

• Cefazolin - Intermediate (I, 4) - not recommended as first-line due to intermediate susceptibility 1

Alternative options (based on susceptibility results):

• Cefepime - Susceptible (S, ≤0.12) 4

  • For complicated UTIs or if oral therapy fails
  • Dosage: 0.5-1 g IV every 12 hours for 7-10 days for mild to moderate infections 4

• Imipenem or Meropenem - Susceptible (S, ≤0.25) 1

  • Reserved for complicated infections or treatment failures
  • Should be used judiciously to prevent development of resistance 5

Duration of Treatment

• For uncomplicated cystitis: 5 days of nitrofurantoin is sufficient 1
• For complicated UTIs: 7-14 days of appropriate antimicrobial therapy 1
• For men when prostatitis cannot be excluded: 14 days of therapy 1

Special Considerations

• This E. coli isolate shows multi-drug resistance (MDR) pattern with resistance to fluoroquinolones and trimethoprim/sulfamethoxazole, which is becoming increasingly common 5
• The presence of cloudy urine with elevated WBCs and positive leukocyte esterase confirms active infection rather than asymptomatic bacteriuria 1
• Fluoroquinolones should be avoided due to confirmed resistance and current guidelines recommend against their empiric use when local resistance rates exceed 10% 1

Follow-up Recommendations

• Routine post-treatment urinalysis or urine cultures are not indicated for asymptomatic patients 1
• If symptoms do not resolve by the end of treatment or recur within 2 weeks, perform another urine culture and antimicrobial susceptibility testing 1
• For recurrent UTIs (≥3 episodes/year), consider prophylactic strategies after completing the current treatment course 1

Common Pitfalls to Avoid

• Do not treat asymptomatic bacteriuria except in specific circumstances (pregnancy, before urological procedures) 1
• Avoid fluoroquinolones despite their convenience due to confirmed resistance and risk of promoting further resistance 1
• Do not use antibiotics with intermediate susceptibility (like cefazolin in this case) when fully susceptible alternatives are available 1
• Carbapenems should be reserved for complicated infections or when no other options exist to prevent development of resistance 5