What are the recommended antibiotics for treating a urinary tract infection (UTI)?

Recommended Antibiotics for Treating Urinary Tract Infections (UTIs)

First-line antibiotics for uncomplicated UTIs in women include nitrofurantoin (5 days), fosfomycin trometamol (single dose), or trimethoprim-sulfamethoxazole (3 days) based on local resistance patterns. 1

Treatment Algorithm for UTIs

Uncomplicated Cystitis in Women

1. First-line options:

   • Nitrofurantoin macrocrystals: 50-100 mg four times daily for 5 days OR
   • Nitrofurantoin monohydrate/macrocrystals: 100 mg twice daily for 5 days OR
   • Fosfomycin trometamol: 3 g single dose OR
   • Pivmecillinam: 400 mg three times daily for 3-5 days 1

2. Alternative options (when first-line agents cannot be used):

   • Trimethoprim-sulfamethoxazole: 160/800 mg twice daily for 3 days (if local E. coli resistance <20%) 1
   • Cephalosporins (e.g., cefadroxil): 500 mg twice daily for 3 days (if local E. coli resistance <20%) 1

UTIs in Men

• Trimethoprim-sulfamethoxazole: 160/800 mg twice daily for 7 days 1
• Fluoroquinolones can be prescribed based on local susceptibility testing 1

Uncomplicated Pyelonephritis

• Fluoroquinolones for 5-7 days OR
• Trimethoprim-sulfamethoxazole for 14 days (based on susceptibility testing) 1
• Third-generation cephalosporins are preferred for management 2

Clinical Considerations

Diagnostic Approach

• Urine culture is recommended for:
  • Suspected pyelonephritis
  • Symptoms that don't resolve or recur within 4 weeks after treatment
  • Women with atypical symptoms
  • Pregnant women 1

Antibiotic Selection Factors

1. Bacterial susceptibility patterns in your local community
2. Efficacy for the specific indication
3. Tolerability and adverse effects
4. Ecological impact (collateral damage to normal flora)
5. Cost and availability 1, 3

Important Caveats

• Fluoroquinolones: Despite high efficacy, they should be reserved for more invasive infections due to adverse effects and increasing resistance 1, 4
• Beta-lactams: Less effective as empiric first-line therapy for uncomplicated cystitis 4
• Asymptomatic bacteriuria: Should not be treated except in pregnant women and patients scheduled for urinary tract procedures 1
• Post-treatment cultures: Not indicated for asymptomatic patients after treatment 1

Treatment Failure

If symptoms don't resolve by end of treatment or recur within 2 weeks:

1. Obtain urine culture with susceptibility testing
2. Assume the infecting organism is resistant to the initial agent
3. Retreat with a 7-day regimen using a different antibiotic 1

Recurrent UTIs

For patients with recurrent UTIs (≥3 UTIs/year or ≥2 in 6 months):

• Try non-antimicrobial interventions first (increased fluid intake, vaginal estrogen in postmenopausal women)
• Consider methenamine hippurate for prevention in women without urinary tract abnormalities
• Continuous or post-coital antimicrobial prophylaxis when non-antimicrobial interventions fail 1

Antimicrobial Resistance Considerations

• E. coli accounts for >75% of bacterial cystitis cases 1
• Increasing resistance to trimethoprim-sulfamethoxazole and fluoroquinolones limits their empiric use in many communities 3
• For suspected resistant pathogens, obtain cultures before starting therapy and adjust based on susceptibility results 1, 3

The choice of antibiotic should be guided by local resistance patterns, patient-specific factors (allergies, pregnancy status, renal function), and antibiotic stewardship principles to minimize the development of resistance.