139.1 🎓 醫孞生版

139.1.0.1 📌 䞀頁重點

  • C. difficile = Gram + 厭氧 spore-forming; toxin A + B 臎 colitis
  • 危險因子: 抗生玠 (clindamycin, FQ, cephalosporin worst), 䜏院, 高霡, PPI, immunocompromised
  • 蚺斷: stool GDH antigen + toxin A/B EIA OR NAAT (PCR for toxin gene) — 2-step algorithm
  • 嚎重床:
    • Non-severe: WBC < 15K, Cr ≀ 1.5x baseline
    • Severe: WBC ≥ 15K, Cr > 1.5x baseline (or > 1.5 mg/dL)
    • Fulminant: hypotension, ileus, megacolon
  • 治療 (2021 IDSA/SHEA):
    • Initial episode (non-severe / severe): Fidaxomicin 200 mg BID × 10 d (preferred) OR Vancomycin PO 125 mg QID × 10 d
    • Fulminant: Vanco PO/NG 500 mg QID + Metronidazole IV 500 mg q8h + surgical consult
    • First recurrence: Fidaxomicin (preferred if not used) or vancomycin taper + bezlotoxumab (anti-toxin B mAb)
    • Multiple recurrences (≥ 2): FMT (fecal microbiota transplant) or Rebyota/Vowst
  • 22E paradigm: metronidazole NOT first-line anymore (inferior)

139.1.0.2 1⃣ Risk Factors

139.1.0.2.1 抗生玠 (最重芁)
  • Highest risk: clindamycin, fluoroquinolones, 3rd-4th gen cephalosporins
  • Lower risk: macrolides, tetracyclines, sulfa
  • Minimal: doxycycline (some protective), nitrofurantoin, fosfomycin
139.1.0.2.2 Host
  • Age ≥ 65
  • Recent hospitalization / LTC
  • GI surgery, NG tube
  • PPI / H2 blocker (controversial but supported)
  • Immunocompromise (HIV, chemo, post-transplant)
  • IBD (ulcerative colitis especially)

139.1.0.3 2⃣ Diagnosis (2-step algorithm)

139.1.0.3.1 Stool Testing (only liquid stool, not formed)
  1. Step 1 — Sensitive screening:
    • GDH antigen (sensitive for C. diff presence)
    • OR PCR (NAAT) for toxin gene
  2. Step 2 — Specific confirmation:
    • Toxin A/B EIA (specific for toxin production = active infection)
  3. 若 GDH+ but toxin EIA−: NAAT (settle “true active” vs colonized)

⚠ Don’t test asymptomatic patients (colonization 20%, mistake for “cured”)

139.1.0.3.2 Imaging (severe / fulminant)
  • CT: colonic wall thickening, “accordion sign”, megacolon
  • Endoscopy: only if dx 䞍確定; pseudomembranes = pathognomonic (~ 50% sensitivity)
  • Avoid in fulminant (perforation risk)

139.1.0.4 3⃣ Severity Classification

嚎重床 Criteria
Non-severe (mild-moderate) WBC < 15,000 + Cr ≀ 1.5x baseline
Severe WBC ≥ 15,000 OR Cr > 1.5x baseline (or > 1.5 mg/dL)
Fulminant (severe complicated) Severe + hypotension OR shock OR ileus OR megacolon

139.1.0.5 4⃣ Treatment (2021 IDSA/SHEA — UPDATED)

139.1.0.5.1 Initial Episode
嚎重床 First-line Alternative
Non-severe Fidaxomicin 200 mg BID × 10 d Vancomycin PO 125 mg QID × 10 d
Severe Fidaxomicin 200 mg BID × 10 d Vancomycin PO 125 mg QID × 10 d
Fulminant Vancomycin PO/NG 500 mg QID + Metronidazole IV 500 mg q8h + Surgical consult (PR vancomycin enema if ileus)
139.1.0.5.2 ⚠ Metronidazole 已退出 first-line
  • 之前 (2010 era): metronidazole first-line
  • 2017 IDSA + 2021 update: metronidazole inferior (only for fulminant adjunct OR in resource-limited)
  • 原因: inferior cure rate + higher recurrence
139.1.0.5.3 First Recurrence
  • Fidaxomicin 200 mg BID × 10 d (if not used initially)
  • OR Vancomycin PO taper + pulse (125 mg QID × 14d → BID × 7d → daily × 7d → q2-3d × 8 wks)
  • Bezlotoxumab (anti-toxin B mAb, 10 mg/kg IV ×1) add-on for high-risk (decreases recurrence 38%)
139.1.0.5.4 Multiple Recurrences (≥ 2)
  • Fecal Microbiota Transplant (FMT): gold standard, > 85% cure
    • Donor screened; colonoscopy / enema / oral capsules
  • Rebyota (RBL) — FDA 2022, fecal microbiota oral suspension (rectal)
  • Vowst (SER-109) — FDA 2023, oral capsule purified Firmicutes spores
  • Bezlotoxumab add-on
  • Long-term suppressive vanco

139.1.0.6 5⃣ Surgical Indications (Fulminant)

  • Refractory to 48 hr medical Tx
  • Megacolon (> 6 cm)
  • Perforation
  • Shock + multi-organ failure
  • Surgery: subtotal colectomy with ileostomy (classic) OR diverting loop ileostomy + colonic lavage (newer)