What is the recommended treatment for E. coli (Escherichia coli) infections?

Treatment of E. coli Infections

For E. coli infections, treatment depends critically on the infection site and pathotype: use trimethoprim-sulfamethoxazole for uncomplicated UTIs (if local resistance <20%), fluoroquinolones or extended-spectrum cephalosporins for pyelonephritis and severe infections, but never use antibiotics for enterohemorrhagic E. coli (EHEC/STEC) as they increase the risk of hemolytic uremic syndrome. 1, 2

Urinary Tract Infections

Uncomplicated Cystitis

• First-line therapy is trimethoprim-sulfamethoxazole 160/800 mg twice daily for 3 days, but only if local resistance rates are below 20%. 1, 2
• Fosfomycin is an alternative single-dose option specifically FDA-approved for uncomplicated UTIs in women caused by E. coli. 3
• Fluoroquinolones (ciprofloxacin 500 mg twice daily for 3 days) are effective alternatives but should be reserved due to increasing resistance concerns. 1

Pyelonephritis

• For outpatient treatment, use fluoroquinolones for 7 days if local resistance is below 10%. 1, 2
• For hospitalized patients, initiate IV therapy with fluoroquinolones, aminoglycosides, extended-spectrum cephalosporins (such as ceftriaxone), or carbapenems. 1, 4
• Treatment duration should be 7-14 days. 1, 2

Severe Infections and Bacteremia

• Use combination therapy with an extended-spectrum penicillin or extended-spectrum cephalosporin plus an aminoglycoside for at least 6 weeks. 1
• Continue combination therapy until susceptibility results are available to ensure adequate coverage. 1
• Ceftriaxone is FDA-approved for bacteremia caused by E. coli and provides broad coverage. 4

Gastrointestinal Infections

Enterotoxigenic E. coli (ETEC)

• Use trimethoprim-sulfamethoxazole 160/800 mg twice daily for 3 days if susceptible, or fluoroquinolones such as ciprofloxacin 500 mg twice daily for 3 days. 2, 5

Enteropathogenic E. coli (EPEC)

• Treatment is similar to ETEC with trimethoprim-sulfamethoxazole or fluoroquinolones. 2

Enterohemorrhagic E. coli (EHEC/STEC)

• Do not use antibiotics for EHEC/STEC infections as they increase Shiga toxin production and the risk of hemolytic uremic syndrome. 1, 2
• This is a critical pitfall to avoid—antibiotics worsen outcomes in bloody diarrhea caused by EHEC/STEC. 1, 2

Critical Considerations for Antimicrobial Selection

Local Resistance Patterns

• Always check local antimicrobial susceptibility patterns before initiating empiric therapy, as E. coli resistance varies considerably between regions. 1, 2
• Resistance rates exceeding 20% are common for ampicillin and trimethoprim-sulfamethoxazole in many regions. 1, 2

Culture and Susceptibility Testing

• Obtain appropriate cultures before starting antibiotics to avoid suboptimal therapy. 1, 2
• When culture and susceptibility information become available, adjust therapy accordingly. 5, 4

Special Populations

• For immunocompromised patients, use longer treatment durations. 1
• In pediatric patients, fluoroquinolones may be justified in special circumstances (such as multidrug-resistant UTIs) after careful risk-benefit assessment. 2

Treatment Duration Summary

• Uncomplicated UTIs: 3 days 1, 2
• Pyelonephritis: 7-14 days 1, 2
• Bacteremia or severe infections: minimum 6 weeks 1, 2

Common Pitfalls to Avoid

• Never use antibiotics for bloody diarrhea without ruling out EHEC/STEC, as this increases hemolytic uremic syndrome risk. 1, 2
• Do not rely on ampicillin or trimethoprim-sulfamethoxazole empirically in areas with high resistance rates (>20%). 1, 2
• Failure to obtain cultures before starting antibiotics leads to suboptimal therapy and missed opportunities for de-escalation. 1, 2
• For severe infections, do not use monotherapy initially—combination therapy is recommended until susceptibilities are known. 1