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

Treatment of Enteroinvasive E. coli (EIEC) Infection

For enteroinvasive E. coli found in stool, treat with either TMP-SMX (160/800 mg twice daily for 3 days) or a fluoroquinolone (ciprofloxacin 500 mg, norfloxacin 400 mg, or ofloxacin 300 mg twice daily for 3 days) as first-line therapy. 1

First-Line Antibiotic Options

The Infectious Diseases Society of America guidelines establish clear treatment protocols for EIEC, which causes dysentery similar to Shigella through invasion of the large bowel mucosa 1, 2:

For immunocompetent patients:

• TMP-SMX 160/800 mg twice daily for 3 days (if susceptible) 1, 3
• OR Fluoroquinolone for 3 days: 1, 3
  • Ciprofloxacin 500 mg twice daily
  • Norfloxacin 400 mg twice daily
  • Ofloxacin 300 mg twice daily

For immunocompromised patients:

• Same regimens but extend duration to 7-10 days 1, 3

Alternative Agents

Azithromycin is an important alternative, particularly when:

• Dysentery is present 3
• Fever accompanies watery diarrhea 3
• Travel to regions with high fluoroquinolone resistance has occurred 3

Azithromycin dosing options: 3

• 500 mg once daily for 3 days
• OR 1 gram single dose (better adherence, though may cause more GI side effects)

Ceftibuten has demonstrated efficacy in pediatric dysentery caused by EIEC, particularly when TMP-SMX resistance is present 4

Critical Clinical Distinction: Rule Out STEC/EHEC

You must differentiate EIEC from Shiga toxin-producing E. coli (STEC/EHEC) before initiating antibiotics. 1, 3

• For STEC/EHEC: Antibiotics are contraindicated as they increase Shiga toxin production and risk of hemolytic uremic syndrome 1, 3
• EIEC causes dysentery through mucosal invasion (similar to Shigella), while STEC causes hemorrhagic colitis through toxin production 2, 5
• EIEC is biochemically atypical (late/no lactose fermentation, lysine decarboxylase negative, non-motile) and shares antigens with Shigella 2

Resistance Considerations

Local resistance patterns should guide initial therapy: 3

• TMP-SMX resistance is increasing globally; in one study, 30% of Shigella strains and 80% of EIEC strains were TMP-SMX-resistant 4
• When TMP-SMX-resistant organisms are treated with TMP-SMX, patients have significantly more stools and watery consistency at days 3-5 compared to effective therapy 4
• Fluoroquinolone resistance is rising in many regions, making azithromycin increasingly valuable 3

Pediatric Considerations

For children with EIEC dysentery:

• Ceftibuten (oral cephalosporin) for 5 days is effective and well-tolerated 4
• TMP-SMX at pediatric dosing (5 mg/kg trimethoprim + 25 mg/kg sulfamethoxazole twice daily for 3 days) 1
• Azithromycin is also appropriate in pediatric patients 3

Common Pitfalls to Avoid

• Do not withhold antibiotics for EIEC dysentery (unlike STEC where antibiotics are contraindicated) 1
• Do not use antimotility agents if STEC cannot be ruled out 1
• Do not assume TMP-SMX susceptibility without testing or knowledge of local resistance patterns 3, 4
• Do not treat for only 1-2 days; minimum 3-day course is required for adequate eradication 1, 3