IM faculty here, One more high-yield topic to share with you. Long post but worth it (Topic 6 of 8). C. diff!
Dropped everything I know about C. diff into one post. This is the version I wish I had before my boards. Save it.
>RISK FACTORS
Antibiotics — any antibiotic, not just broad-spectrum. Biggest trigger.
Older age, IBD, solid organ transplant, GI surgery
PPIs — possible association, boards love testing this
Incubation up to 3 months after antibiotic use, always ask carefully
>>Alcohol hand gel does NOT kill spores. Soap and water ONLY. This is tested.
>PRESENTATION
Watery diarrhea (rarely bloody), fever, crampy pain, leukocytosis, ↑Cr
Fulminant: toxic megacolon, ileus, hypotension, shock → needs surgery consult
>DIAGNOSIS
Only test unformed stool, no laxatives, ≥3 new stools/day. Testing formed stool = classic trap.
NAAT (PCR)
Best test. Sensitive + specific. Sufficient alone when stool criteria met.
EIA toxin A+B
Specific but not sensitive. Used in multistep approach.
GDH EIA
Sensitive, not specific. Screening step only — always pair with toxin.
Multistep (GDH + toxin ± NAAT)
Use when stool submission criteria aren't strictly met.
>Do NOT retest asymptomatic patients after treatment. PCR stays + for weeks = meaningless.
>INITIAL TREATMENT
Stop the offending antibiotic if possible. Fidaxomicin > vancomycin (lower recurrence). Metronidazole is dead as first-line.
Nonsevere
Fidaxomicin 200 mg BID × 10d (preferred)
Vancomycin 125 mg QID × 10d (alternative)
Metronidazole 500 mg TID × 10–14d (only if above unavailable)
Severe : WBC ≥15k or Cr ≥1.5
Fidaxomicin 200 mg BID × 10d (preferred)
Vancomycin 125 mg QID × 10d (alternative)
Fulminant: shock / hypotension / toxic megacolon / ileus
Vancomycin 500 mg QID PO or NGT
+ Metronidazole 500 mg q8h IV
If ileus → add Vancomycin 500 mg PR q6h
→ Surgical evaluation. No exceptions.
RECURRENT C. DIFF
25% of patients relapse. Each episode ↑ risk of the next.
1st recurrence
Fidaxomicin 200 mg BID × 10d (preferred)
Vancomycin taper: QID × 10–14d → BID × 7d → QD × 7d → q2–3d × 2–8 wk
2nd+ recurrence
Fidaxomicin BID × 10d or extended pulse
Vancomycin taper (as above)
Vancomycin × 10d → Rifaximin 400 mg TID × 20d
Fecal microbiota products, FDA approved (oral capsule or rectal suspension)
ONE-LINERS
-Soap and water only, alcohol gels don't kill spores
-Fidaxomicin preferred for ALL severities over vancomycin
-Metronidazole = last resort only (not even second-line anymore)
-Fulminant = vanco PO/NGT + IV metro ± vanco PR + surgery consult
-No loperamide. No antimotility. Ever.
-Don't retest stool in asymptomatic patients after treatment
-Fecal microbiota products = FDA approved for recurrent CDI prevention
If you want more details, refer to my Substack here. I post regularly over there but will continue to post here periodically!
Johnson, S., Lavergne, V., Skinner, A. M., Gonzales-Luna, A. J., Garey, K. W., Kelly, C. P., & Wilcox, M. H. (2021). Clinical Practice Guideline by the Infectious Diseases Society of America (IDSA) and Society for Healthcare Epidemiology of America (SHEA): 2021 Focused Update Guidelines on Management of Clostridioides difficile Infection in Adults. Clinical infectious diseases : an official publication of the Infectious Diseases Society of America, 73(5), e1029–e1044. https://doi.org/10.1093/cid/ciab549