Antibiotic Treatment for Colitis

The choice of antibiotic depends entirely on the type of colitis: for C. difficile colitis use oral vancomycin 125 mg four times daily for 10 days in severe disease or oral metronidazole 500 mg three times daily for 10 days in mild-moderate disease; for inflammatory bowel disease (ulcerative colitis or Crohn's disease), antibiotics are generally not indicated except for specific complications. 1, 2

Oral metronidazole 500 mg three times daily for 10 days is the first-line treatment 1, 2
Metronidazole should be limited to initial episodes of non-severe disease 1
If the colitis was clearly antibiotic-induced and the patient is stable, consider stopping the inciting antibiotic and observing for 48 hours, but monitor closely for deterioration 1

Oral vancomycin 125 mg four times daily for 10 days is superior to metronidazole and is the treatment of choice 1, 2, 3
Vancomycin can be increased to 500 mg four times daily in fulminant cases (hypotension, shock, ileus, or megacolon), though evidence for higher dosing is limited 1
Metronidazole use in severe CDI is strongly discouraged 1

Fidaxomicin 200 mg orally twice daily for 10 days is an alternative to vancomycin, particularly useful for patients at high risk for recurrence (elderly, multiple comorbidities, concurrent antibiotics) 1, 2
Note: Fidaxomicin was not associated with fewer recurrences in PCR ribotype 027 strains 1
Teicoplanin 100 mg twice daily can serve as an alternative to vancomycin where available 2

For first recurrence: fidaxomicin or vancomycin with pulse/taper strategy 1
For multiple recurrences failing antibiotic therapy: fecal microbiota transplantation (FMT) is strongly recommended 1
Bezlotoxumab (monoclonal antibody) may prevent recurrences, especially in 027 strain, immunocompromised patients, or severe CDI 1

Discontinue the inciting antibiotic immediately if possible 1, 2
If continued antibiotic therapy is required for another infection, use agents less associated with CDI: parenteral aminoglycosides, sulfonamides, macrolides, vancomycin, or tetracycline/tigecycline 1
Avoid antiperistaltic agents and opiates entirely in suspected infectious colitis 2
Early surgical consultation for patients with systemic toxicity; consider total colectomy or diverting loop ileostomy with colonic lavage for fulminant colitis 1

No antibiotic regimen can be recommended in general for ulcerative colitis 2
Antibiotics are not part of standard treatment for ulcerative colitis 1
One small observational study suggested potential benefit of broad-spectrum antibiotics in severe non-toxic ulcerative colitis after corticosteroid failure, but this is not guideline-supported 4

Metronidazole 10-20 mg/kg/day has a role in selected patients with colonic or treatment-resistant disease, though not recommended as first-line due to side effects 1
Concomitant intravenous metronidazole is often advisable with IV steroids for severe disease, as it may be difficult to distinguish active disease from septic complications 1
Broad-spectrum antibiotics are indicated for suppurative complications: abscesses, fistulas, and localized peritonitis due to microperforation 2
No antibiotic regimen can be recommended in general for Crohn's disease 2

For uncomplicated left-sided diverticulitis in immunocompetent patients without systemic manifestations, antibiotics should be avoided entirely 2
Antibiotics are recommended for localized complicated diverticulitis with pericolic air or fluid 2

Antibiotic therapy must target Gram-negative bacilli and anaerobic bacteria 2
For critically ill patients with sepsis, early use of broader-spectrum antimicrobials is essential 2

Never use oral metronidazole or vancomycin for severe CDI systemically—these are for oral use only in CDI 3
Monitor renal function in patients >65 years receiving oral vancomycin, as nephrotoxicity can occur even with oral administration 3
Do not assume all colitis is infectious—inflammatory bowel disease requires different management and antibiotics may not help 1, 2
Recurrence rates for CDI are 5-50% after treatment; consider this when counseling patients 5
Post-treatment carriage of C. difficile is common and does not require retreatment unless symptomatic 6