4 - Clostridioides difficile Flashcards
Is C. difficile gram positive or negative?
Gram positive
What shape is C. difficile
Rod
How does C. difficile respire?
Obligate anaerobe
What does C. difficile smell like?
Slightly sweet, barnyard
What medium is used to isolate C. difficile?
Cycloserine-cefoxitin fructose agar (CCFA)
What are the stages of sporulation?
- Limited nutrient environment
- Phosphorylated Spo0A induces expression of sigma factor H
- Sigma factor forms a feed-forward loop with Spo0A resulting in asymmetric division.
- SpoA activates sigma factor F in forespore.
- Sigma factor F causes a cascade of compartment-specific alternative sigma factor activation.
- Mother cell engulfs forespore in cytoplasmic double membrane, further layers added to form mature spore.
- Cell lysis - mature spore released
What are the stages in spore germination?
Products of cspBAC operon control germination:
- primary bile acids interact with CspC -> CspC activates CspB - CspB cleaves pro-SleC into active SleC (lytic enzyme) -> SleC degrades cortex -> Core rehydrates and elongates -> Vegetative cell exits endospore
How do Toxins A and B enter cells?
- TcdA and TcdB attach cell surface receptor CROP domain and enter via endocytosis
- Acidification of endosome causes conformational change in CDP domain forming a pore in the endosomal membrane
- Translocation of glucosyltransferase domain into cytosol.
- Inactivation of Ras and Rho family GTPases.
What pathogenesis is caused by toxins A and B
Tight junction disruption - inflammation
Neutrophil infiltration - fluid secretion causing diarrhoea
Pro-inflammatory cytokine production by macrophages and dendritic cells - inflammation, fluid secretion and diarrhoea
Cell death - Pseudomembranous plaque formation and necrosis
How does CDT enter cells?
- CDTb attaches to cell surface receptor and binds CDTa
- Internalised by endocytosis
- Acidification of endosome causes conformational change in CDTb
- Pore formed in endosomal membrane
- CDTa translocated into the cytosol
- ADP-ribosylation-mediated inhibition of actin polymerisation
What pathogenesis is caused by CDT
Loss of cytoskeletal structure - malabsorption and disrupted fluid balance
Increased microtubule formation - enhanced C. difficile adherence
What is a hypervirulent clone of C. difficile?
Fluoroquinolone resistant type - ribotype 027
What are the two fecal microbiota transplants used to treat C. difficile?
Rebiotix - rectal installation two doses
Vowst - oral administration 4 capsules a day for 3 days
