Empiric Antibiotic Treatment for Infectious Colitis
For infectious colitis, empiric treatment should be based on the suspected pathogen, with metronidazole 500 mg three times daily orally for 10 days as first-line therapy for non-severe C. difficile colitis and vancomycin 125 mg four times daily orally for 10 days for severe C. difficile colitis. 1
Pathogen-Specific Empiric Treatment
C. difficile Colitis
- Non-severe C. difficile colitis: Metronidazole 500 mg three times daily orally for 10 days 1, 2
- Severe C. difficile colitis: Vancomycin 125 mg four times daily orally for 10 days 1, 2
- Recurrent C. difficile colitis: Vancomycin 125 mg four times daily orally for at least 10 days or fidaxomicin 200 mg twice daily for 10 days 1, 2
- Teicoplanin 100 mg twice daily can be used as an alternative to oral vancomycin if available 1
Bacterial Infectious Colitis (non-C. difficile)
- For febrile dysenteric diarrhea: Single dose of azithromycin 1000 mg empirically when invasive bacterial enteropathogens (Shigella, Salmonella, and Campylobacter) are suspected 3
- For mild-to-moderate community-acquired intra-abdominal infections: Ticarcillin-clavulanate, cefoxitin, ertapenem, moxifloxacin, or tigecycline as single-agent therapy 4
- Alternative regimen: Metronidazole combined with cefazolin, cefuroxime, ceftriaxone, cefotaxime, levofloxacin, or ciprofloxacin 4
Severity Assessment for C. difficile Colitis
Non-severe C. difficile colitis criteria 1, 2:
- Stool frequency < 4 times daily
- No signs of severe colitis
- White blood cell count < 15 × 10^9/L
Severe C. difficile colitis criteria 1, 2:
- Fever, rigors, hemodynamic instability
- Signs of peritonitis or ileus
- Marked leukocytosis
- Elevated serum creatinine or lactate
- Pseudomembranous colitis on endoscopy
Special Considerations
Treatment Duration
- For C. difficile colitis: 10 days is standard treatment duration 1, 5
- For other bacterial colitis: 7-10 days is typically recommended 4
- After adequate source control in complicated intra-abdominal infections, a short course (3-5 days) of antibiotics may be sufficient 4
Important Precautions
- Avoid antiperistaltic agents and opiates in C. difficile infection 1, 2
- Discontinue the inciting antibiotic if possible 1, 6
- Monitor renal function in patients >65 years receiving oral vancomycin 5
- Be aware that ciprofloxacin has been associated with acute pancreatitis in approximately 3% of patients treated for infectious colitis 7
Treatment Failures and Complications
- Consider colectomy for perforation of the colon, systemic inflammation with deteriorating clinical condition not responding to antibiotics, toxic megacolon, or severe ileus 1, 2
- Relapses occur in up to 24% of C. difficile cases treated with vancomycin 8
- For patients with ongoing signs of peritonitis beyond 5-7 days of antibiotic treatment, diagnostic investigation is warranted to determine if additional surgical intervention is necessary 4
Antibiotic Selection Considerations
- Local resistance patterns should guide empiric therapy, particularly for fluoroquinolones due to increasing E. coli resistance 4
- For health care-associated infections, obtain cultures from the site of infection, particularly in patients with prior antibiotic exposure 4
- Standard stool culture should be performed in all patients with suspected infectious colitis 3
- When Shiga toxin-producing E. coli (STEC) is suspected, avoid antibiotics and test for E. coli O157:H7 and Shiga toxin directly in stool 3