What is the treatment for Entero-invasive Escherichia coli (E. coli) infection?

Treatment of Enteroinvasive E. coli (EIEC) Infection

For enteroinvasive E. coli infections, treatment with trimethoprim-sulfamethoxazole (TMP-SMX) 160/800 mg twice daily for 3 days or a fluoroquinolone such as ciprofloxacin 500 mg twice daily for 3 days is recommended as first-line therapy, assuming the organism is susceptible.

Understanding Enteroinvasive E. coli

Enteroinvasive E. coli (EIEC) is a pathotype of E. coli that causes an illness similar to shigellosis. EIEC:

• Invades the epithelial cells of the large intestine
• Causes inflammation and ulceration of the mucosa
• Often presents with symptoms of bacillary dysentery
• Is biochemically atypical compared to other E. coli (may ferment lactose late or not at all, is lysine decarboxylase negative, and non-motile) 1

First-Line Treatment Options

According to the Infectious Diseases Society of America guidelines, the recommended treatments for EIEC are:

1. TMP-SMX: 160/800 mg twice daily for 3 days (if susceptible) 2
2. Fluoroquinolones:
   • Ciprofloxacin 500 mg twice daily for 3 days
   • Ofloxacin 300 mg twice daily for 3 days
   • Norfloxacin 400 mg twice daily for 3 days 2

The FDA label for TMP-SMX confirms its indication for shigellosis, which has a similar pathogenesis to EIEC 3. Similarly, ciprofloxacin is indicated for infectious diarrhea caused by E. coli 4.

Treatment Algorithm

1. Assess severity:

   • Mild to moderate disease: Oral antibiotics
   • Severe disease (high fever, significant bloody diarrhea, dehydration): Consider IV antibiotics initially

2. Antibiotic selection:

   • First-line: TMP-SMX or fluoroquinolone (based on local resistance patterns)
   • Alternative if contraindicated: Azithromycin

3. Duration:

   • Standard course: 3 days for uncomplicated infection
   • Extended course (7-10 days): For immunocompromised patients 2

4. Supportive care:

   • Fluid replacement
   • Electrolyte correction
   • Avoid antimotility agents as they may worsen invasive infections

Special Considerations

Antibiotic Resistance

Local resistance patterns should guide therapy. In areas with high TMP-SMX resistance, fluoroquinolones may be preferred as first-line therapy. However, fluoroquinolone resistance is increasing globally, particularly in Campylobacter species and now other enteric pathogens 2.

Pediatric Patients

For children, ciprofloxacin is not a first-choice drug due to concerns about joint/cartilage toxicity 4. TMP-SMX is generally preferred if the organism is susceptible, or azithromycin may be considered as an alternative.

Severe Disease

In cases of severe dysentery with complications such as significant gastrointestinal bleeding, hypovolemic shock, or co-infection (as reported in a case of EIEC with rotavirus co-infection), intravenous antibiotics, fluid resuscitation, and possibly blood transfusions may be required 5.

Pitfalls to Avoid

1. Delaying treatment in severe cases or immunocompromised patients
2. Using antimotility agents which can worsen invasive infections by delaying clearance of the organism
3. Failing to consider local resistance patterns when selecting empiric therapy
4. Treating for too short a duration in immunocompromised patients (should be treated for 7-10 days rather than the standard 3 days) 2
5. Not obtaining cultures in severe or persistent cases to guide targeted therapy

EIEC infections should be treated promptly with appropriate antibiotics to reduce the duration of illness, prevent complications, and limit transmission to others.