clostridioides difficile infection
C. difficile infection ≥3 unformed stools in 24 h + positive toxin test, usually within 8 weeks of antibiotics. Test only unformed stool. Stop the inciting antibiotic and PPI where possible. Oral vancomycin or fidaxomicin — never metronidazole first-line for inpatients, never IV vancomycin. Fulminant disease (shock, ileus, megacolon) → high-dose PO vancomycin + IV metronidazole + surgical consult. Recurrence (~25%) → fidaxomicin or vancomycin taper-pulse; FMT from the second recurrence.
C. difficile infection initial bundle
- contact precautions; soap-and-water hand hygiene (alcohol does not kill spores)
- stop inciting antibiotics if possible; narrow any that must continue
- stop PPI unless clear indication; avoid loperamide and opioids
- first episode: vancomycin 125 mg PO QID × 10 days (or fidaxomicin 200 mg PO BID × 10 days)
- fulminant (shock, ileus, megacolon): vancomycin 500 mg PO/NG QID + metronidazole 500 mg IV q8h; + rectal vancomycin if ileus
- fulminant: general surgery + ID consult
- no test of cure; do not retest within 7 days
Formulary access, not resistance, drives CDI drug choice in Canada — check local fidaxomicin restrictions and oral vancomycin preparation.
diagnosis
- test only if ≥3 unformed stools in 24 h without laxatives in the past 48 h
- two-step testing (GDH or PCR, then toxin EIA) — PCR alone detects colonisation
- PCR+/toxin− → likely colonisation; treat only if strong clinical suspicion
- do not test formed stool, asymptomatic patients, or for test of cure
- CT: colonic wall thickening, pericolonic stranding; plain film/CT for megacolon (>6 cm) or perforation
severity
| category | criteria (IDSA/SHEA) |
|---|---|
| non-severe | WBC ≤15 × 10⁹/L and creatinine <133 µmol/L |
| severe | WBC >15 × 10⁹/L or creatinine ≥133 µmol/L |
| fulminant | hypotension/shock, ileus, or megacolon |
treatment
first episode
| agent | dose | notes |
|---|---|---|
| fidaxomicin | 200 mg PO BID × 10 days | IDSA/SHEA 2021 preferred — lower recurrence (Louie (2011)); cost ~$2,500, restricted in many Canadian hospitals |
| vancomycin | 125 mg PO QID × 10 days | Sunnybrook first-line for all inpatients; capsules not ODB-covered (EAP request) — oral solution compounded from IV vials is a cheaper route |
| metronidazole | 500 mg PO TID × 10 days | only for non-severe outpatient disease when vancomycin/fidaxomicin unavailable |
IV vancomycin does not reach the colon — never used for CDI.
fulminant
- vancomycin 500 mg PO/NG QID
-
- metronidazole 500 mg IV q8h
- ileus → rectal vancomycin 500 mg in 100 mL saline q6h retention enema
- early surgical consult: subtotal colectomy or diverting loop ileostomy with colonic lavage; lactate rising or WBC very high → do not delay
recurrence
Recurrence = symptoms returning within 8 weeks of completing therapy.
| episode | options |
|---|---|
| first recurrence | fidaxomicin 200 mg PO BID × 10 days, or extended-pulsed (BID × 5 days → alternate days to day 25) — EXTEND (2018); or vancomycin taper-pulse if vancomycin used initially |
| second or later recurrence | fidaxomicin, vancomycin taper-pulse, or vancomycin 10 days → rifaximin 400 mg TID × 20 days; then FMT |
Vancomycin taper-pulse: 125 mg QID × 14 days → BID × 7 days → daily × 7 days → every 2–3 days for 2–8 weeks.
- bezlotoxumab (MODIFY (2017)) reduced recurrence but was discontinued by the manufacturer in January 2025
- FMT after ≥2 recurrences; ID/GI referral
prevention
- antimicrobial stewardship — the dominant modifiable risk
- deprescribe PPIs
- contact precautions until ≥48 h after diarrhoea resolves
- secondary prophylaxis with oral vancomycin during future antibiotic courses: weak evidence; consider for patients with multiple prior recurrences (practice varies)
- probiotics: not recommended by IDSA/SHEA
traps
- testing formed stool or patients on laxatives → treating colonisation
- metronidazole first-line for inpatients — inferior to vancomycin at all severities
- IV vancomycin for CDI — ineffective
- repeat testing after treatment — toxin and PCR stay positive for weeks
- ileus with little diarrhoea can be fulminant CDI — absence of diarrhoea does not exclude it
- fulminant CDI: surgical outcomes worsen as lactate and WBC climb — consult early, not after failure of medical therapy
- continuing a non-essential antibiotic or PPI → higher recurrence