What are the recommended antibiotics for treating infectious colitis?

Antibiotic Treatment for Infectious Colitis

For infectious colitis caused by C. difficile, oral vancomycin 125 mg four times daily for 10 days or fidaxomicin 200 mg twice daily for 10 days are the recommended first-line treatments, with vancomycin being strongly preferred over metronidazole, especially for severe cases. 1

Treatment Based on Pathogen

Clostridioides difficile Infection (CDI)

Severity-Based Treatment Algorithm:

1. Non-severe CDI:

   • Oral vancomycin 125 mg four times daily for 10 days OR
   • Fidaxomicin 200 mg twice daily for 10 days 1
   • Metronidazole 500 mg three times daily for 10 days may be used only when access to vancomycin or fidaxomicin is limited 1

2. Severe CDI (WBC ≥15,000 cells/mL or serum creatinine >1.5 mg/dL):

   • Oral vancomycin 125 mg four times daily for 10 days OR
   • Fidaxomicin 200 mg twice daily for 10 days 1

3. Fulminant CDI (hypotension, shock, ileus, or megacolon):

   • Vancomycin 500 mg orally or via nasogastric tube four times daily PLUS
   • Intravenous metronidazole 500 mg every 8 hours
   • If ileus present: add rectal vancomycin 500 mg in 100 mL normal saline every 6 hours 1

For Recurrent CDI:

• First recurrence: If metronidazole was used initially, switch to vancomycin 125 mg four times daily for 10 days 1
• Multiple recurrences: Consider tapered/pulsed vancomycin regimen, fidaxomicin, bezlotoxumab as adjunctive therapy, or fecal microbiota transplantation 1

Other Bacterial Causes of Infectious Colitis:

• For Shigella, Salmonella, and Campylobacter: Azithromycin 1000 mg single dose is recommended for empiric treatment of febrile dysenteric diarrhea in adults 2
• For Staphylococcus aureus enterocolitis: Oral vancomycin 500 mg to 2 g daily in 3-4 divided doses for 7-10 days 3

Special Considerations

Pediatric Dosing:

• For C. difficile and staphylococcal enterocolitis: 40 mg/kg/day of oral vancomycin in 3-4 divided doses for 7-10 days (not to exceed 2 g daily) 3

Monitoring During Treatment:

• Monitor clinical response during the first 5-6 days of treatment
• Consider changing to vancomycin if deterioration or lack of response occurs 1
• For patients >65 years: Monitor renal function during and after vancomycin treatment due to potential nephrotoxicity 3
• Monitor for recurrence for up to 2 months after treatment 1

Important Precautions:

• Discontinue the inciting antibiotic as soon as possible to reduce recurrence risk 1
• Implement infection control measures: hand hygiene with soap and water (not alcohol-based sanitizers), contact precautions, isolation, and thorough environmental cleaning 1
• For vancomycin: Be aware of potential systemic absorption in patients with inflammatory intestinal disorders or renal insufficiency 3
• Watch for severe dermatologic reactions with vancomycin (TEN, SJS, DRESS, AGEP, LABD) 3

Treatment Pitfalls to Avoid

1. Using metronidazole as first-line for severe CDI: Metronidazole has inferior efficacy and risk of neurotoxicity with repeated courses 1

2. Using IV vancomycin alone for CDI: It does not achieve adequate concentrations in the gut lumen 1

3. Failing to discontinue the inciting antibiotic: This increases recurrence risk 1

4. Inadequate infection control measures: C. difficile spores require soap and water for removal, not alcohol-based sanitizers 1

5. Overlooking risk factors for severe disease: Age >60 years, fever, hypoalbuminemia, peripheral leukocytosis, ICU stay, and abnormal abdominal CT findings 1

6. Prolonged or repeated metronidazole courses: Can cause potentially irreversible neurotoxicity 1

7. Not testing for C. difficile in IBD flares: CDI can mimic or trigger IBD flares 1