What is the treatment approach for infectious colitis?

Treatment Approach for Infectious Colitis

For infectious colitis, the treatment approach depends critically on identifying the causative pathogen: discontinue offending antibiotics if possible, initiate pathogen-specific antimicrobial therapy for all bacterial causes except Shiga toxin-producing E. coli (STEC), provide supportive care with fluid resuscitation and electrolyte replacement, and avoid antiperistaltic agents which can worsen outcomes.

Initial Diagnostic and Supportive Management

Immediate Assessment

• Obtain stool studies including multiplex PCR followed by guided culture on PCR-positive pathogens to confirm active infection while providing isolates for antibiotic susceptibility testing 1
• Standard stool culture should be performed looking specifically for Shigella, Salmonella, Campylobacter, STEC, and Clostridioides difficile 2
• When STEC is suspected (acute dysentery with low-grade or absent fever), the laboratory must look for E. coli O157:H7 and Shiga toxin directly in stool 2
• Check for recent antibiotic exposure, which should prompt immediate testing for C. difficile 3

Supportive Care

• Provide oral hydration for mild-to-moderate symptoms; escalate to nasogastric or intravenous fluid and electrolyte replacement for severe illness to correct dehydration and electrolyte imbalances 3
• Avoid antiperistaltic agents and opiates, as these can precipitate toxic megacolon and worsen outcomes 4
• Antiemetic, antimotility, and antisecretory drugs may be used cautiously for symptom control in appropriate cases 3

Pathogen-Specific Antimicrobial Therapy

Clostridioides difficile Infection (CDI)

Discontinue the inciting antibiotic immediately if possible, as continued antibiotic use significantly increases CDI recurrence risk 4

Initial Episode - Mild to Moderate CDI

• Metronidazole 500 mg orally three times daily for 10 days for initial mild-moderate episodes 4
• Vancomycin 125 mg orally four times daily for 10 days is an alternative 4, 5

Initial Episode - Severe CDI

• Vancomycin 125 mg orally four times daily for 10 days is superior to metronidazole and should be used for severe disease 4, 5
• For fulminant CDI (hypotension/shock, ileus, or megacolon), increase vancomycin to 500 mg orally four times daily 4
• If oral therapy is impossible: metronidazole 500 mg IV three times daily plus intracolonic vancomycin 500 mg in 100 mL normal saline every 4-12 hours and/or vancomycin 500 mg four times daily by nasogastric tube 4

Recurrent CDI

• For first recurrence, use the same treatment as initial episode based on severity 4
• For second and subsequent recurrences: vancomycin 125 mg orally four times daily for at least 10 days, followed by a taper/pulse strategy (decreasing daily dose by 125 mg every 3 days, then 125 mg every 3 days for 3 weeks) 4
• Fidaxomicin 200 mg orally twice daily for 10 days is particularly useful for high-risk patients (elderly with multiple comorbidities receiving concomitant antibiotics) 4
• Fecal microbiota transplantation (FMT) is effective for multiple recurrences after failed appropriate antibiotic treatments 4
• Bezlotoxumab (monoclonal antibody) may prevent recurrences in patients with CDI due to epidemic strain 027, immunocompromised patients, and those with severe CDI 4

Surgical Intervention for CDI

• Colectomy should be performed for: perforation of the colon, systemic inflammation with deteriorating clinical condition not responding to antibiotics, toxic megacolon, or severe ileus 4
• Surgery should preferably be performed before colitis becomes very severe; serum lactate >5.0 mmol/L is a marker indicating urgent surgical consultation 4

Other Invasive Bacterial Enteropathogens

Empiric Therapy for Febrile Dysenteric Diarrhea

• For suspected Shigella, Salmonella, or Campylobacter: azithromycin 1000 mg orally as a single dose 2
• Once pathogen is identified, tailor antimicrobial therapy based on culture and susceptibility results 2

STEC Infection

• Do NOT use antibiotics for STEC infection, as antimicrobial therapy can increase risk of hemolytic uremic syndrome 2
• Provide supportive care only with careful monitoring for complications 2

Parasitic Infections

• Antimicrobial therapy is indicated for confirmed parasitic infections 3
• Specific agents depend on the identified parasite from specialized stool studies 2

Infection Control Measures for CDI

• Place patients in private rooms with en suite hand washing and toilet facilities; cohort nursing is acceptable if private rooms unavailable 4
• Hand hygiene must be performed with soap and water, NOT alcohol-based sanitizers, as alcohol does not kill C. difficile spores or remove them from hands 4
• Use contact precautions with thorough cleaning and disinfection of environment and patient equipment 4

Monitoring and Follow-up

• Monitor for treatment response: stool frequency should decrease or consistency improve within 3 days, with no new signs of severe colitis 4
• Treatment failure is defined as absence of response after 3 days 4
• Monitor serum vancomycin concentrations in patients with renal insufficiency, colitis, or those receiving concomitant aminoglycosides when using oral vancomycin 5
• In patients >65 years of age, monitor renal function during and after vancomycin treatment to detect nephrotoxicity 5

Critical Pitfalls to Avoid

• Never delay treatment while awaiting stool microbiology results in severely ill patients 4
• Never use antibiotics for STEC infection 2
• Never use alcohol-based hand sanitizers alone for C. difficile - soap and water handwashing is mandatory 4
• Never continue unnecessary antibiotics in patients with CDI, as this significantly increases recurrence risk 4
• If continued antibiotic therapy is required for another infection, use agents less frequently associated with CDI: parenteral aminoglycosides, sulfonamides, macrolides, vancomycin, or tetracycline/tigecycline 4