What is the recommended treatment for a patient with infective colitis?

Treatment of Infective Colitis

For confirmed infectious colitis, pathogen-specific antimicrobial therapy should be initiated immediately for all bacterial causes except Shiga toxin-producing E. coli (STEC), while supportive care with IV fluids, electrolyte replacement, and thromboprophylaxis forms the foundation of management. 1, 2

Immediate Diagnostic Workup

Before initiating treatment, establish the specific pathogen through:

• Standard stool culture for invasive bacterial pathogens (Shigella, Salmonella, Campylobacter, C. difficile) 1
• Direct testing for E. coli O157:H7 and Shiga toxin when STEC is suspected (characterized by acute dysentery with low-grade or absent fever) 1
• Multiplex PCR followed by guided culture on PCR-positive pathogens to confirm active infection and provide isolates for antibiotic susceptibility testing 2
• Flexible sigmoidoscopy with biopsy to confirm diagnosis and exclude cytomegalovirus infection, which requires specific treatment 3
• Stool assay for C. difficile toxin, as this pathogen is more prevalent in severe colitis and associated with increased morbidity and mortality 3

Supportive Care (All Patients)

Regardless of pathogen, all patients with infectious colitis require:

• IV fluid and electrolyte replacement to correct and prevent dehydration, with potassium supplementation of at least 60 mmol/day (hypokalaemia can promote toxic dilatation) 3
• Subcutaneous low-molecular-weight heparin for thromboprophylaxis, as risk of thromboembolism is increased during infectious flares 3
• Correction of anemia if present 3
• Nutritional support if the patient is malnourished, preferably via enteral route (associated with fewer complications than parenteral nutrition: 9% vs 35%) 3
• Withdrawal of anticholinergic, anti-diarrheal, NSAID, and opioid drugs 3

Pathogen-Specific Antimicrobial Therapy

For Invasive Bacterial Pathogens (Shigella, Salmonella, Campylobacter)

• Empiric treatment with azithromycin 1000 mg single dose for adults with febrile dysenteric diarrhea when invasive bacterial enteropathogens are suspected 1
• Adjust therapy based on culture and susceptibility results once available 1, 2

For C. difficile Infection

• Oral vancomycin 125 mg four times daily for 10 days is the recommended treatment 4
• If oral vancomycin was used for first episode, consider fidaxomicin 200 mg twice daily for 10 days for first recurrence 3
• Add oral vancomycin therapy if C. difficile is detected, and consider stopping immunosuppressive therapy if possible (though this may not always be warranted) 3

For STEC (E. coli O157:H7)

• Antimicrobial therapy is contraindicated for STEC infections, as antibiotics may increase risk of hemolytic uremic syndrome 1
• Supportive care only with close monitoring for complications 1

Critical Monitoring Parameters

Monitor the following to identify patients requiring escalation of care:

• Vital signs four times daily (pulse rate, temperature) 3
• Stool chart recording number, character, and presence of blood 3
• Laboratory tests every 24-48 hours: FBC, ESR or CRP, serum electrolytes, serum albumin 3
• Plain abdominal radiography if colonic dilatation suspected (transverse colon diameter >5.5 cm indicates severe disease) 3

When to Distinguish from Inflammatory Bowel Disease

A critical pitfall is delaying treatment while awaiting stool microbiology results when severe colitis is present. 3 If acute onset colitis is difficult to distinguish from inflammatory bowel disease and the patient meets criteria for severe disease, treatment with IV corticosteroids should not be delayed until stool cultures return 3. However, this applies only when inflammatory bowel disease cannot be excluded—once infectious colitis is confirmed, corticosteroids are contraindicated and pathogen-directed antimicrobial therapy is required 1, 2.

Indications for Surgical Consultation

Maintain close liaison with a colorectal surgeon for patients with:

• Evidence of colonic dilatation despite maximal therapy (absolute indication for colectomy) 5
• Clinical deterioration despite appropriate antimicrobial therapy 2
• Complications such as perforation, toxic megacolon, or exsanguinating hemorrhage 6