C Diff

Question 1

What is the treatment for C diff?

Answer 1

• Metronidazole (possibly less effective)
• Vancomycin (good colonic levels and efficacy in severe disease BUT high ‘collateral damage’ as broad spectrum)
• Fidaxomicin (narrow spectrum so reduced ‘collateral damage’ translating to lower relapse rate; BUT expensive)
• Monoclonal Ab against toxin (Bezlotoxumab reduces recurrence rates when combined with antibiotic treatment NEJM 2017)
• Surgery
• Faecal transplant (endoscopic either upper or lower GI, but ?capsule delivery in future)

Question 2

What is behind the pathogenesis of C diff?

Answer 2

1. Reduced colonisation resistance (risk factors: antibiotic exposure, older age, ?PPI use)
2. Colonic colonisation with C diff (risk factors: antibiotic exposure, hospitalisation)
3. Toxin production

Question 3

How is diagnosis of C diff infection made?

Answer 3

Positive screening test AND toxin essay WITH compatible clinical picture
Diarrhoea = passage of 3 or more loose or liquid stools per day or more frequently than is for normal for patient
2 step test
- SENSITIVE screening test GDH Ag ELISA PCR
- SPECIFIC toxin essay

Question 4

How do you interpret positive Ag and negative toxin result?

Answer 4

Equivocal results can be due to:

• non toxigenic C diff
• cross reaction with other organism
• toxin level too low to detect (in which case toxin level should increase on repeat test)
• non-viable C diff

Question 5

How do you treat recurrent C diff infection?

Answer 5

First recurrence
- vancomycin
- fidaxomicin
- faecal transplant
Second recurrence
- vancomycin followed by pulsed/tapered course
- faecal transplant
- fidaxomicin
Third recurrence
- faecal transplant