What is the treatment for a patient with a positive Enzyme Immunoassay (EIA) for Cytotoxin A and B?

Treatment for Positive EIA for Cytotoxin A and B

Initiate treatment with oral vancomycin 125 mg four times daily for 10 days as first-line therapy for confirmed Clostridioides difficile infection (CDI). 1

Diagnostic Confirmation

A positive EIA for toxins A and B confirms active CDI and warrants immediate treatment, as this indicates the presence of toxin-producing bacteria causing symptomatic disease. 1

• EIA toxin positivity is diagnostic when combined with clinical symptoms (≥3 unformed stools in 24 hours) and represents true infection requiring treatment. 1
• Patients with positive toxin EIA have higher rates of severe disease, complications, and recurrence compared to those who are toxin-negative but PCR-positive. 2, 3
• The specificity of toxin EIA ranges from 96-100%, making false positives rare, though sensitivity is lower (60-90%). 1

Treatment Approach Based on Disease Severity

Initial Episode - Mild to Moderate Disease

• Oral vancomycin 125 mg four times daily for 10 days is the preferred first-line agent. 4, 1
• Clinical success rates with vancomycin are 81-88% at end of treatment. 4
• Median time to diarrhea resolution is 4-5 days. 4

Initial Episode - Severe Disease

Severe disease is defined by: white blood cell count ≥15,000 cells/mm³ OR serum creatinine ≥1.5 mg/dL. 1

• Oral vancomycin 125 mg four times daily for 10 days remains first-line therapy. 1, 4
• Consider fidaxomicin 200 mg twice daily for 10 days as an alternative, particularly for patients at high risk for recurrence, as it demonstrates superior sustained response rates (70-72% vs 57% with vancomycin). 1, 5

Fulminant Disease

Fulminant disease indicators include: hypotension, shock, ileus, toxic megacolon, WBC >30,000 cells/mm³, or peritoneal signs. 1

• Oral vancomycin 500 mg four times daily PLUS intravenous metronidazole 500 mg every 8 hours. 1
• Add rectal vancomycin 500 mg in 100 mL normal saline as enema every 6 hours if ileus is present. 1
• Surgical consultation is mandatory; consider colectomy if no improvement after 6 days of medical therapy. 1

Recurrent CDI Management

Recurrence occurs in 18-25% of patients after initial treatment. 4, 6

First Recurrence

• Repeat the same regimen used for initial episode if non-severe (oral vancomycin 125 mg four times daily for 10 days). 1, 7
• Fidaxomicin 200 mg twice daily for 10 days is preferred for first recurrence due to lower subsequent recurrence rates (13% vs 24% with vancomycin). 1, 5

Second or Subsequent Recurrence

• Tapered and pulsed vancomycin regimen: 125 mg four times daily for 10-14 days, then twice daily for 7 days, then once daily for 7 days, then every 2-3 days for 2-8 weeks. 1, 7
• Fidaxomicin 200 mg twice daily for 10 days is an alternative. 1, 5
• Fecal microbiota transplantation should be considered for multiple recurrences. 1, 7

Risk Factors for Recurrence

High-risk patients who may benefit from fidaxomicin over vancomycin include those with: 6

• Age >65 years (particularly >77 years)
• Emergency hospital admission
• Recent hospitalization (4-12 weeks prior)
• Elevated C-reactive protein at diagnosis
• Previous gastrointestinal ward admissions
• CDI diagnosed at hospital admission

Critical Pitfalls to Avoid

• Do not use metronidazole as first-line therapy for initial CDI, as vancomycin demonstrates superior efficacy. 1
• Do not repeat stool testing during the same episode or within 7 days of treatment completion, as this does not improve diagnostic yield and may detect asymptomatic colonization. 1
• Do not test asymptomatic patients or those without diarrhea, as up to 10-30% of long-term care facility residents are asymptomatically colonized. 1
• Implement strict hand hygiene with soap and water rather than alcohol-based sanitizers, as alcohol does not inactivate C. difficile spores. 1
• Discontinue inciting antibiotics whenever possible, as continued antibiotic use increases risk of treatment failure and recurrence. 1