What are the first-line antibiotics for treating cystitis caused by E. coli (Escherichia coli)?

First-Line Antibiotics for E. coli Cystitis

Nitrofurantoin monohydrate/macrocrystals (100 mg twice daily for 5 days) is the preferred first-line antibiotic for treating uncomplicated cystitis caused by E. coli due to its minimal resistance patterns and limited collateral damage to normal flora. 1

Recommended First-Line Options

• Nitrofurantoin monohydrate/macrocrystals: 100 mg twice daily for 5 days is highly effective with minimal resistance development and limited ecological impact on normal flora 1
• Fosfomycin trometamol: 3 g single dose is appropriate where available, though it may have slightly inferior efficacy compared to standard short-course regimens 1
• Pivmecillinam: 400 mg three times daily for 3-5 days is recommended in regions where available (primarily European countries) 1

Alternative Options Based on Local Resistance Patterns

• Trimethoprim-sulfamethoxazole: 160/800 mg twice daily for 3 days can be used if local E. coli resistance rates are below 20% or if the specific isolate is known to be susceptible 1
  • Historically the traditional first-line agent in the US, but rising resistance rates have reduced its utility 1
  • In European countries, resistance rates range from 14.6% to 60%, limiting its empiric use 2

Second-Line Options

• Fluoroquinolones (ciprofloxacin, levofloxacin, ofloxacin): While highly efficacious in 3-day regimens, these should be reserved for situations where first-line agents cannot be used due to concerns about promoting resistance 1

  • Resistance rates are increasing globally, especially in developing countries (55.5-85.5%) compared to developed countries (5.1-32.0%) 2

• β-Lactams (amoxicillin-clavulanate, cefdinir, cefaclor, cefpodoxime-proxetil): These can be used for 3-7 days when other recommended agents cannot be used 1

  • Generally have inferior efficacy and more adverse effects compared to other UTI antimicrobials 1
  • A study comparing cefpodoxime to ciprofloxacin found cefpodoxime did not meet criteria for noninferiority 3

Antibiotics to Avoid

• Amoxicillin or ampicillin: Should not be used for empirical treatment due to poor efficacy and very high prevalence of antimicrobial resistance worldwide 1

Clinical Considerations

• Local resistance patterns should guide therapy choice, particularly for trimethoprim-sulfamethoxazole 1, 2
• Urine culture is not routinely needed for uncomplicated cystitis but should be performed if symptoms do not resolve or recur within 4 weeks after treatment 1
• For patients whose symptoms do not resolve by the end of treatment or recur within 2 weeks, urine culture with susceptibility testing should be performed 1

Treatment Algorithm

1. First choice: Nitrofurantoin monohydrate/macrocrystals (100 mg twice daily for 5 days) 1, 4
2. If nitrofurantoin contraindicated: Fosfomycin trometamol (3 g single dose) 1, 4
3. If local resistance to TMP-SMX <20%: Consider trimethoprim-sulfamethoxazole (160/800 mg twice daily for 3 days) 1
4. If all first-line options unavailable: Consider β-lactams or fluoroquinolones, recognizing their limitations and potential for promoting resistance 1

Common Pitfalls to Avoid

• Using fluoroquinolones as first-line therapy despite their high efficacy, as this promotes resistance to these important agents needed for more serious infections 1, 4
• Prescribing trimethoprim-sulfamethoxazole empirically without knowledge of local resistance patterns 1, 5
• Using amoxicillin or ampicillin empirically due to high resistance rates 1, 2
• Failing to adjust therapy if symptoms persist, which may indicate resistance to the chosen antibiotic 1