What is the appropriate treatment for a patient with a urinary tract infection (UTI) caused by Escherichia coli (E. coli), as indicated by a urine culture showing greater than 100,000 Colony-Forming Units per milliliter (CFU/mL)?

Treatment for E. coli Urinary Tract Infection Based on Culture and Sensitivity

Based on the culture and sensitivity results showing E. coli resistant to cefazolin, ceftriaxone, ciprofloxacin, and levofloxacin, the most appropriate treatment is nitrofurantoin or amoxicillin-clavulanate for 7-10 days. 1, 2

Interpretation of Urinalysis and Culture Results

• The urinalysis shows clear signs of infection with 2+ leukocyte esterase, 20-40 WBCs/HPF, many bacteria, and trace protein/ketones, confirming an active urinary tract infection 1
• Culture results show >100,000 CFU/mL of E. coli, which meets the diagnostic threshold for a significant UTI 1
• The sensitivity pattern shows resistance to:
  • Cefazolin (R)
  • Ceftriaxone (R)
  • Ciprofloxacin (R)
  • Levofloxacin (R)
  • Trimethoprim/sulfamethoxazole (R) 1

Treatment Algorithm

First-line options (based on sensitivity results):

1. Nitrofurantoin (S): 100 mg PO BID for 7 days

   • Excellent sensitivity profile (0.9-2.6% resistance) 3, 4
   • Achieves high urinary concentrations 5
   • Not suitable for pyelonephritis or systemic infection 1

2. Amoxicillin-clavulanate (S): 875/125 mg PO BID for 7-10 days

   • Effective for both lower and upper UTIs 1, 5
   • Higher resistance rates than nitrofurantoin (36.9%) but still susceptible in this case 3

Alternative options (based on sensitivity results):

1. Cefepime (S): 1-2 g IV every 12 hours for 7-10 days

   • FDA-approved for complicated and uncomplicated UTIs 2
   • Reserved for severe infections or when oral therapy isn't appropriate 2

2. Gentamicin (S): 5 mg/kg IV/IM daily

   • Effective but potential for nephrotoxicity limits use 5
   • Consider for severe infection if other options aren't feasible 1

3. Meropenem or Imipenem (S): Reserved for severe infections only

   • Should be preserved for more resistant infections 5
   • Not first-line despite 100% sensitivity 3

Duration of Therapy

• 7-10 days is the recommended duration for uncomplicated UTIs 1
• Longer courses (10-14 days) may be needed for:
  • Complicated infections
  • Pyelonephritis
  • Male patients
  • Elderly patients with multiple comorbidities 1

Important Clinical Considerations

• Fluoroquinolones (ciprofloxacin, levofloxacin) should be avoided due to:

  • Demonstrated resistance in this patient 1
  • Increasing resistance rates (up to 49.9% for ciprofloxacin) 3, 6
  • FDA warnings about serious adverse effects 5

• Cephalosporins: First and third-generation options (cefazolin, ceftriaxone) show resistance in this case, making them inappropriate choices 5

• Trimethoprim-sulfamethoxazole: Resistance in this isolate precludes its use despite being a common UTI treatment 3, 4

Follow-up Recommendations

• Clinical improvement should occur within 48-72 hours of appropriate therapy 1
• Consider repeat urinalysis if symptoms persist beyond 72 hours 1
• No imaging is typically needed for uncomplicated UTIs that respond to treatment 1
• Consider urologic evaluation if:
  • Recurrent infections (≥3 in 12 months)
  • Rapid recurrence after treatment
  • Presence of anatomic abnormalities 1

Prevention Strategies

• Adequate hydration
• Urination after sexual intercourse
• Avoiding spermicidal products
• Consider vaginal estrogen in postmenopausal women 1