What is the recommended treatment for Shiga toxin-producing Escherichia coli (STEC) infections, particularly in high-risk patients such as young children and the elderly?

Treatment of STEC Infections

Do not give antibiotics to patients with STEC infections—antibiotics are contraindicated and increase the risk of hemolytic uremic syndrome (HUS) and death. 1, 2

Antibiotic Avoidance: The Critical Safety Principle

The Infectious Diseases Society of America explicitly states that antibiotics cause harm in STEC infections. This applies to all age groups and all STEC strains that produce Shiga toxin 2:

• Avoid fluoroquinolones, β-lactams, trimethoprim-sulfamethoxazole, and metronidazole in all patients with STEC O157 or non-O157 STEC producing Shiga toxin 2 due to evidence of harm 1, 2
• Avoid macrolide antibiotics despite limited data, as insufficient evidence of benefit exists and some evidence suggests harm 1, 2
• The mechanism of harm is antibiotic-induced bacterial lysis, which increases Shiga toxin release and subsequent systemic toxin exposure 2
• Multiple retrospective studies demonstrate higher rates of HUS in patients treated with antimicrobials 3

Critical pitfall: Because the Shiga toxin profile is often unknown when treatment decisions are made, and because no clear benefit exists for treating less virulent STEC infections with antibiotics, avoidance of antibiotic treatment is recommended for all suspected STEC cases 1

Primary Treatment: Aggressive Volume Expansion

Early and aggressive intravenous fluid administration is the only therapeutic intervention proven to reduce morbidity and mortality. 2, 3

Fluid Management Protocol

• Initiate early parenteral volume expansion during the diarrhea phase before HUS develops—this significantly reduces the risk of oligoanuric renal failure in children who subsequently develop HUS 2, 3
• Dehydration at admission is independently associated with increased need for dialysis in post-diarrheal HUS 2
• For mild to moderate dehydration: Use reduced osmolarity oral rehydration solution (ORS) as first-line therapy 3
• For severe dehydration, shock, altered mental status, or failure of oral rehydration: Administer isotonic intravenous fluids such as lactated Ringer's or normal saline 3

Hyperhydration Strategy (Emerging Evidence)

An ongoing multinational trial is evaluating a hyperhydration protocol that includes:

• Hospitalization of all eligible children with high-risk STEC 4
• Administration of 200% maintenance balanced crystalloid fluids 4
• Target goals: 10% weight gain and 20% reduction in hematocrit 4

While this aggressive approach is under investigation, the principle of early and generous volume expansion is already supported by current guidelines 2, 3

Monitoring for Complications

High-Risk Populations

• Children aged <5 years have the highest incidence of STEC infection and highest risk for HUS 1, 2, 5
• Approximately 8% of patients with O157 STEC infection develop HUS, characterized by thrombocytopenia, hemolytic anemia, and renal failure 1, 2, 5
• Shiga toxin 2 (stx2) genes are associated with increased risk of both bloody diarrhea and HUS compared to Shiga toxin 1 2

Clinical Assessment

Look for these specific features that increase STEC O157 risk:

• Bloody diarrhea (present in ~90% of STEC patients who develop HUS) 2
• Abdominal tenderness 2
• Absence of fever (particularly suggestive when bloody diarrhea is present) 1, 2
• Peripheral white blood cell count >10,000 cells/µL (present in ~65% of E. coli O157 patients) 2

Laboratory Monitoring

• Complete blood count: Monitor for thrombocytopenia, hemolytic anemia with schistocytes, and hematocrit changes 2
• Renal function: Track creatinine, blood urea nitrogen, and urine output for early detection of HUS 2
• Hydration status: Volume depletion is a frequently identified risk factor for diarrhea-related deaths and complications 2

Medications to Avoid

Antimotility Agents

• Do not use loperamide or other antimotility agents in suspected or documented STEC infections 1, 3
• Clinical conditions have worsened following administration of antimotility agents to patients with STEC infections 1
• Antimotility agents may increase the risk of HUS 1, 3

Anticholinergic Medications

• Limited reports suggest that routine use of medications with anticholinergic properties may lead to increased risk of severe outcomes, including death, from toxin-mediated diarrheal illnesses 1

Supportive Care Only

The cornerstone of management is supportive care with careful fluid management, while avoiding interventions that may worsen outcomes 3, 6:

• Close monitoring for development of HUS is essential, particularly in children under 5 years 3
• Approximately half of affected patients require dialysis 7
• Renal replacement therapy (RRT) should be initiated when indicated by standard criteria 6

Special Considerations

Immunocompromised Patients

For immunocompromised patients with severe illness and bloody diarrhea, the decision to use empiric antibacterial treatment is complex:

• The risks of HUS development must be carefully weighed against the risks of untreated bacterial infection 3
• If STEC is suspected or confirmed, antibiotics should still be avoided 1

Asymptomatic Contacts

• Asymptomatic contacts of people with STEC infection should not receive antimicrobial therapy 3

Prognosis and Extrarenal Complications

Beyond renal involvement, STEC HUS can affect multiple organ systems 7:

• Neurological complications: Altered mental status, seizures, stroke, and coma
• Gastrointestinal manifestations: Hemorrhagic colitis, bowel ischemia/necrosis, and perforation
• Pancreatic involvement: Pancreatitis and beta cell dysfunction resulting in acute or chronic insulin-dependent diabetes mellitus
• Cardiac complications: Thrombotic microangiopathy in cardiac microvasculature and troponin elevation
• Musculoskeletal involvement: Rhabdomyolysis

Extrarenal complications occur not only acutely but may also manifest well after recovery from the acute phase of HUS 7