Clostridium difficile associated illnesses

Question 1

Describe the morphology of C diff

Answer 1

Anaerobic, spore-forming, gram negative rod. It is a major cause of nosocomial infectious diarrhea

Question 2

What are the 6 stages of disease brought about by a C diff infection?

Answer 2

Colonization, exposure to antibiotics, disruption of intestinal microflora, proliferation of C diff and toxin production, damage to intestinal epithelium, diarrhea and other diseases

Question 3

What is required for C diff to be virulent?

Answer 3

C diff must have two toxin genes or else it is an avirulent strain

Question 4

Describe how C diff can take over the gut from normal gut microflora

Answer 4

Antibiotic exposure can select for C diff, by eliminating competition

Question 5

What effect does C diff have on epithelial cells? How is this effect caused?

Answer 5

C diff causes a cytopathic effect in gut epithelial cells by inhibiting small GTPases which causes actin cytoskeleton rearrangement and epithelial cell rounding

Question 6

What are the 2 approaches that need to be done to detect pathogenic C diff in the laboratory?

Answer 6

Detection of C diff using culture and EIAs

Detection of toxins using EIAs, cell culture cytotoxicity neutralization assay, NAATs

Question 7

How can C diff be cultured/detected? (2)

Answer 7

Cultured on CCFA (cefoxitin cycloserine fructose agar)

EIA with common antigen (glutamate dehydrogenase)

Question 8

Why do culture and detection tests for C diff need to be confirmed?

Answer 8

Because either virulent or non-virulent strains can be detected (non-virulent: no toxins produced)

Question 9

What is the purpose of a toxin immunoassay for C diff?

Answer 9

To detect the presence of toxin in a sample

Question 10

What is a cell culture cytotoxicity neutralization assay for and how does it work?

Answer 10

To detect the presence of toxin in a smear. Works by looking for a cytopathic effect on a smear of cells which could mean C diff toxin is causing the effect. To confirm this, you need to make a duplicate smear with the antitoxin and if the cytotoxic effect dissipates, then that probably means the effect was being caused by the toxin

Question 11

What is another method for the detection of C diff toxin?

Answer 11

Real time PCR