What antibiotics are used to treat a urinary tract infection (UTI) in an otherwise healthy adult?

Antibiotic Treatment for Urinary Tract Infections in Healthy Adults

For uncomplicated UTIs in otherwise healthy adult women, use fosfomycin 3g single dose, nitrofurantoin 100mg twice daily for 5 days, or pivmecillinam 400mg three times daily for 3-5 days as first-line therapy. 1

First-Line Antibiotics for Women with Uncomplicated Cystitis

The 2024 European Association of Urology guidelines provide clear first-line options: 1

• Fosfomycin trometamol 3g single dose - recommended only for women with uncomplicated cystitis 1
• Nitrofurantoin - multiple formulations available:
  • Macrocrystals: 50-100mg four times daily for 5 days 1
  • Monohydrate or macrocrystals: 100mg twice daily for 5 days 1
  • Prolonged release: 100mg twice daily for 5 days 1
• Pivmecillinam 400mg three times daily for 3-5 days 1

These agents maintain excellent activity against E. coli, the most common uropathogen, with resistance rates below 15% in recent surveillance data. 2

Alternative Antibiotics When First-Line Options Are Unsuitable

Use these alternatives only when first-line agents are contraindicated or local resistance patterns favor them: 1

• Cephalosporins (e.g., cefadroxil) 500mg twice daily for 3 days - only if local E. coli resistance is <20% 1
• Trimethoprim 200mg twice daily for 5 days - avoid in first trimester of pregnancy 1
• Trimethoprim-sulfamethoxazole 160/800mg twice daily for 3 days - avoid in last trimester of pregnancy 1

Critical caveat: Trimethoprim-sulfamethoxazole and fluoroquinolones have high resistance rates in many communities, precluding their use as empiric therapy. 3 Recent data show resistance rates for trimethoprim at 21.4% and cotrimoxazole at 19.3% in recurrent UTIs. 2

Treatment for Men with UTI

All UTIs in men are considered complicated and require longer treatment: 1

• Trimethoprim-sulfamethoxazole 160/800mg twice daily for 7 days 1
• Fluoroquinolones may be prescribed according to local susceptibility testing 1
• The 7-day duration is mandatory as prostatitis cannot be reliably excluded clinically 4

When to Avoid Fluoroquinolones

Do not use fluoroquinolones empirically if: 4

• Local resistance rates exceed 10% 1, 4
• Patient used fluoroquinolones in the last 6 months 4
• Patient is from a urology department (higher resistance risk) 4

The FDA-approved levofloxacin for complicated UTIs at various dosing regimens, but resistance concerns limit its empiric use. 5

Symptomatic Therapy Alternative

For women with mild to moderate symptoms, ibuprofen may be considered as an alternative to antibiotics after patient consultation. 1 This approach reduces antibiotic exposure and resistance development. 1

When Urine Culture Is Mandatory

Obtain urine culture before treatment in these situations: 1

• Suspected acute pyelonephritis 1
• Symptoms not resolving or recurring within 4 weeks after treatment 1
• Atypical symptoms 1
• Pregnancy 1
• Male patients 4

Treatment Failure Management

If symptoms persist after completing therapy: 1

• Obtain urine culture and susceptibility testing 1
• Assume the organism is resistant to the initial agent 1
• Retreat with a 7-day course using a different antibiotic class 1
• Consider imaging to rule out obstruction or abscess if fever persists beyond 72 hours 4

Common Pitfalls to Avoid

• Never use trimethoprim-sulfamethoxazole empirically without knowing local resistance patterns - resistance exceeds 20% in many areas 3, 2
• Do not treat asymptomatic bacteriuria - routine post-treatment cultures are not indicated for asymptomatic patients 1
• Avoid fluoroquinolones for uncomplicated cystitis - reserve these for complicated infections when susceptibility is confirmed 3
• Do not underdose or shorten treatment duration in men - all male UTIs require minimum 7 days of therapy 1, 4