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Clostridioides difficile Infection

GI

Source: IDMP View on spectrum chart →
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Clinical scenario / source

Annotations only — chart still shows the full chemistry of each drug.

1. Clinical Syndrome

Diarrhea (≥3 unformed stools per 24 h) with positive C. difficile testing (toxin EIA + NAAT, or NAAT alone in appropriate clinical context). Includes initial episode (non-severe, severe, fulminant) and recurrence (relapse within 8 weeks of treatment).

Severity stratification (CDI-specific, not the standard severity tier):

  • Non-severe: WBC <15,000 + Cr <1.5 mg/dL
  • Severe: WBC ≥15,000 OR Cr ≥1.5 mg/dL
  • Fulminant: hypotension / shock / ileus / megacolon

Excludes: asymptomatic carriage (don't test, don't treat), other antibiotic-associated diarrhea, ileus without diarrhea (consider fulminant CDI in obtunded ICU patients).

2. Pathogens

Consider the patient: Recent antibiotics (especially fluoroquinolones, clindamycin, broad cephalosporins, carbapenems — highest C. diff risk), age >65, hospitalization, PPI use, IBD, immunocompromise.

Consider the case: Severity (WBC, Cr), recurrence number, ileus / toxic megacolon (CT abdomen if fulminant), inciting antibiotic — stop it if at all possible.

3. Empiric Therapy

TierFirst choiceAlternativesDurationComments
Outpatient
  • 200 mg · PO BID · PO · 10 days

    IDSA 2021 first-line. Lower recurrence vs vancomycin.

  • 125 mg · PO QID · PO · 10 days

    PO formulation only — IV vancomycin doesn't reach the colon.

  • 500 mg · PO TID · PO · 10–14 days

    **Only if fidaxomicin and PO vancomycin unavailable.** No longer first-line monotherapy (IDSA 2017/2021).

10 daysNon-severe initial episode (WBC <15k, Cr <1.5). Stop the inciting antibiotic if possible.
Admitted to ward
  • 200 mg · PO BID · PO · 10 days
  • 125 mg · PO QID · PO · 10 days
10 daysSevere disease (WBC ≥15k or Cr ≥1.5). **No metronidazole monotherapy** for severe disease.
Admitted to ICU
  • 500 mg · PO/NG QID · PO · ≥10 days, often longer
  • 500 mg · IV q8h · IV

    IV adjunct ONLY for fulminant disease with ileus (oral access compromised).

  • 500 mg in 100 mL saline as retention enema · PR q6h · topical

    Rectal vancomycin if ileus prevents PO/NG delivery.

≥10 days; longer per responseFulminant CDI: hypotension, ileus, toxic megacolon. **Urgent surgical consult** for colectomy or diverting loop ileostomy with vancomycin lavage.

4. Directed Therapy

Stop the inciting antibiotic if possible — even partial reduction reduces recurrence. Do NOT do test of cure — PCR can stay positive for weeks; testing asymptomatic patients leads to overtreatment.

Recurrence management:

  • First recurrence: fidaxomicin 200 mg PO BID × 10 d (preferred even if vanco was first-line) or vancomycin pulse-taper × 6+ weeks (125 mg PO QID × 10–14 d → BID × 7 d → daily × 7 d → q2–3 d × 2–8 weeks)
  • Multiple recurrences: fidaxomicin standard or extended-pulse + bezlotoxumab (anti-toxin B mAb) + consider FMT (fecal microbiota transplant) — refer to GI/ID

Fulminant: surgical consult early. Total colectomy or diverting loop ileostomy with vancomycin lavage.

5. Monitoring

Resolution: stool frequency improvement (most patients improve within 5 days), WBC, Cr, lactate, abdominal exam (rule out toxic megacolon).

Track for recurrence in 8 weeks — recurrence is common (~20% after first episode, ~40% after first recurrence).

Toxicity: vancomycin PO and fidaxomicin both well-tolerated (no significant toxicity due to negligible absorption). Metronidazole prolonged → peripheral neuropathy.

Pearls

Stop the inciting antibiotic. No test of cure. No IV metronidazole monotherapy for severe disease — must add PO/NG vancomycin. CDI severity is WBC + Cr based, not BP or vitals based (until fulminant). Hypervirulent NAP1/027 strain associated with worse outcomes — fluoroquinolone resistance is a marker.

References