PathoFinal

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  1. What is C. diff's method of action?
    -both toxins glucosylate (+ glucose)  a threonine residue on G proteins (which control many cell processes) .

    -control polymerization / depolymerization of actin -pseudopodia etc -- requires constant turnover. 

    • -G protein cycle btwn 2 states. 
    • (bind GDP and GTP mediates effects of protein)
  2. Why are G proteins important?
    • control cell processes 
    • control polymerization/depolymerization of actin -pseudopodia etc - requires constant turnover. 
    • cycles btwn GDP and GTP
  3. Where does the A and B toxin act on the GDP-bound form ?
    the threonine residue (that's exposed to be glucosylated)

    -in GTP form the threonine is buried in protein and inaccessible to toxin
  4. What is the result of action of A and B toxin?
    reduces GTPase activity of protein and increases release of GTP from GTP-bond form (glucosylated-GTP bound form has a lower affinity for GTP)
  5. Control of toxin gene expression
    • tcdA /tcdB toxin genes are located on PaLoc pathogenicity island present in all toxogenic strains.
    • Under the control of regulatory genes tcdC (down) and tcdR (up)
    • Toxin levels highest in late-exponential phase of growth
    • Transcription and expression of tcdR is highest in early exponential phase leading to expression of A and B toxins
    • • When toxins build up to highest level, tcdC is expressed which counters tcdR decreasing the expression of the toxin
    • tremendous energy expenditure - 5% of total protein (in-vitro pure cultures) - very powerful toxins and small amounts can cause severe reactions.
    • What do the bacteria get in return for this
    • Why should there be this control – more toxin the better ???
    • - Nutrients
  6. How do you treat C. diff?
    -replace antibiotic causing problem w/ vancomycin or metronidazole (kills c.diff but doesn't affect norman flora)
  7. How do you prevent C. diff?
    at early diagnosis (antibiotic associated diarrhea), monitor for A & B toxins in feces.
  8. What's an alternative therapy for C.diff?
    -replace resident flora using enema containing dilute feces 4rm fam. member.

    (use fecal bacteriotherapy/ fecal micriobiota transplantation (FMT))
  9. What is an enema?
    procedure of introducing liquids into rectum and colon via anus
  10. What are the historical potential reasons for increased CDAD ?
    • changes in underlying host susceptibility 
    • changes in antimicrobial prescribing
  11. What are the recent potential reasons for increased CDAD?
    • new strain w/ increased virulence 
    • (CDT-binary toxin)
    • variations in TcdB activity 
    • changes in infection control practices
  12. What is PulseNet?
    detection of Foodborne Disease by Pulsed-Field Electrophoresis (PFGE)
  13. What organisms are made up of spirochetes?
    Treponema pallium & syphilis
  14. What are the characterisitics of spirochetes?
    • Gram (-)
    • Thin helical
    • Motile, corkscrew style of movement
    • Internal flagella
  15. What are organisms that are spirochetes?
    • Borrelia burgdorferi - Lyme Disease 
    • Treponema pallidum - Syphilis
  16. What is the morphology of spirochetes?
    Peptidoglycan btwn 2 membranes
  17. What is the physiology and motility of spirochetes?
    • has a protoplasmic cylinder
    • 1 to many internal flagella emerge 4rm poles (endoflagella)
    • covered by multilayered, flexible membrane (outer sheath)
  18. How does the motility work for spirochetes?
    • endoflagella rotate -protoplasmic cylinder is rigid and outer sheath is flexible. When flagella rotate in same direction, the protoplasmic cylinder rotates in opposite direction. 
    • this tension placed on cell causes flexing, twisting, jerky corkscrew movement. 
    • effective in viscous solution, blood and tissues.
  19. What disease has similar progression to Lyme Disease?
    -Syphilis; both caused by spirochetes (but diff genera)
  20. What do Lyme Disease and Syphilis have in common?
    multiple stages in their life cycles
Author
ID
312807
Card Set
PathoFinal
Description
11-16 (C.diff:CDAD and PMC)
Updated
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