Treatment of E. coli Infections
For pan-sensitive E. coli systemic infections including bacteremia, ciprofloxacin is the preferred first-line agent in patients with normal renal function, while severe systemic infections and endocarditis require ampicillin 2 g IV every 4 hours plus gentamicin 1.7 mg/kg every 8 hours. 1, 2
Treatment Algorithm Based on Infection Site and Severity
Systemic Infections and Bacteremia
- Ciprofloxacin is first-line for susceptible E. coli systemic infections in patients with normal renal function 1, 2
- For severe systemic infections or endocarditis, use ampicillin 2 g IV every 4 hours plus gentamicin 1.7 mg/kg every 8 hours 1, 2
- Treat bacteremia for 7-14 days 1, 2
- In severe sepsis, initiate combination therapy (beta-lactam plus aminoglycoside) until susceptibilities confirm pan-sensitivity, then de-escalate to monotherapy 1
Urinary Tract Infections
- Aminoglycosides (gentamicin 5-7 mg/kg/day) are appropriate for complicated UTIs 1, 2
- Treat uncomplicated UTI for 3-7 days 1, 2
- Treat complicated UTI for 5-7 days 1, 2
Intra-Abdominal Infections
- For mild-to-moderate community-acquired infections: cefazolin, cefuroxime, ceftriaxone, or cefotaxime combined with metronidazole 2
- Alternative regimen: amoxicillin/clavulanate 1.2-2.2 g every 6 hours 1
- Alternative regimen: ceftriaxone 2 g every 24 hours plus metronidazole 500 mg every 6 hours 1
- For critically ill patients with community-acquired infections: piperacillin/tazobactam 4.5 g every 6 hours, or cefepime 2 g every 8 hours plus metronidazole 500 mg every 6 hours 1
- Treat for 5-7 days 2
Critical Antimicrobial Stewardship Principles
- Avoid carbapenems, piperacillin-tazobactam, or fourth-generation cephalosporins for pan-sensitive organisms to preserve these agents for resistant pathogens 1, 2
- Once susceptibilities confirm pan-sensitivity, de-escalate to narrow-spectrum monotherapy for most infections 1, 2
- Empiric enterococcal coverage is NOT necessary for community-acquired intra-abdominal E. coli infections 1, 2
- Quinolones should not be used unless local E. coli susceptibility is ≥90% due to increasing resistance 1
Critical Pitfalls to Avoid
- Verify actual susceptibility testing to confirm "pan-sensitive" status (susceptible to ampicillin, first-generation cephalosporins, and fluoroquinolones) 1, 2
- Aminoglycosides should not be used as monotherapy except for urinary tract infections due to toxicity concerns 1, 2
- Consider the infection source: biliary and intra-abdominal sources require anaerobic coverage in addition to E. coli coverage 1, 2
- Combination therapy (beta-lactam plus aminoglycoside) demonstrates synergy and is particularly important for endocarditis 1, 2
- For bloody diarrhea caused by Shiga toxin-producing E. coli (STEC), avoid antibiotics due to increased risk of hemolytic uremic syndrome 3