How do I treat a patient with a stool sample positive for Shiga toxin (STx)?

Management of Shiga Toxin-Positive Stool Samples

For patients with stool samples positive for Shiga toxin, supportive care is the recommended treatment approach, with avoidance of antibiotics and antidiarrheal medications which may increase the risk of hemolytic uremic syndrome (HUS). 1

Understanding Shiga Toxin-Producing E. coli (STEC)

Shiga toxin-producing Escherichia coli (STEC) cause approximately 100,000 illnesses, 3,000 hospitalizations, and 90 deaths annually in the United States 1. These infections can lead to:

• Hemorrhagic colitis (bloody diarrhea)
• Hemolytic uremic syndrome (HUS) - a life-threatening condition characterized by thrombocytopenia, hemolytic anemia, and renal failure
• Potential long-term kidney damage and other complications

Treatment Algorithm

1. Initial Management

• Avoid antibiotics: Antibiotics may increase the risk of HUS in patients infected with STEC 1
• Avoid antidiarrheal medications: These can worsen the illness 1
• Provide aggressive hydration: Early parenteral volume expansion may decrease renal damage and improve outcomes 1
• Monitor for complications: Especially in high-risk patients (children <5 years, elderly)

2. Risk Stratification Based on Toxin Profile

Patients with the following profiles have higher risk for developing HUS 2:

• E. coli O157 with Shiga toxin 2 (stx2)
• Non-O157 STEC with stx2 only
• Children under 5 years of age with these profiles

3. Monitoring Parameters

• Complete blood count (CBC)
• Renal function tests
• Electrolytes
• Urinalysis
• Signs of dehydration

4. Hospitalization Criteria

Consider hospitalization for:

• Severe dehydration
• Bloody diarrhea with evidence of systemic toxicity
• Young children (<5 years) with high-risk STEC profiles
• Elderly patients
• Immunocompromised individuals
• Patients with abnormal laboratory values suggesting early HUS

Special Considerations

High-Risk Patients

• Children under 5 years of age have the highest risk of developing HUS 2
• Elderly patients are also at increased risk for severe complications
• Patients with stx2-producing strains have higher risk of severe disease 1

Warning Signs of HUS

Educate patients/families to seek immediate medical attention for:

• Decreased urine output
• Unusual tiredness
• Pallor
• Easy bruising or bleeding
• Neurological symptoms (irritability, seizures, altered consciousness)

Public Health Considerations

• All STEC isolates should be forwarded to public health laboratories for additional characterization 1
• Food service workers and children/staff in childcare settings may require proof of negative cultures before returning to work/school

Emerging Therapies

While not yet standard of care, research is exploring:

• Monoclonal antibodies against Shiga toxins 3
• Toxin receptor analogs 4
• Vaccination strategies 4

Common Pitfalls to Avoid

1. Using antibiotics: Despite being a bacterial infection, antibiotics may increase toxin production and release, potentially worsening outcomes 1, 4

2. Prescribing antidiarrheal medications: These can prolong toxin exposure in the intestine and worsen the clinical course 1

3. Inadequate hydration: Early and aggressive hydration is critical to prevent renal damage 1

4. Delayed monitoring: Patients with STEC infections, especially those with high-risk profiles, require close monitoring for development of HUS

5. Failing to educate patients/families: Clear instructions about warning signs requiring immediate medical attention are essential

Remember that early identification and proper supportive care are the cornerstones of management for patients with STEC infections to prevent progression to HUS and other serious complications.