MMI 301: Listeriosis/Diphtheria

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MMI 301: Listeriosis/Diphtheria
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2013-10-31 15:26:15
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MMI 301
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  1. Listeria's Namesake
    Joseph Lister
  2. Monocyte
    Mononuclear leukocytes that infiltrate during infection
  3. Listeria Morphology
    • -Small gram-positive rod
    • -Facultative anaerobic
    • -Motile at 25 degree and below
    • -Beta-Hemolysis/Catalase (+)
    • -Grow at 4 degrees and in high salt
  4. Listerial Diseases in Pregnant Women:
    Minor febrile gastroenteritis, bacteremia, spontaneous abortion
  5. Listerial Diseases in Neonates/fetus:
    meningitis, death
  6. Listerial diseases in the Immunosuppressed
    meningitis, sepsis, death
  7. Listerial diseases in healthy adults
    rarely: bacteremia, sepsis, CNS infection, minor febrile gastroenteritis
  8. Diagnosing Listeria
    • Positive Gram Stain
    • Cold enrichment
    • Motility
    • beta-Hemolysis
  9. Sources of Listerial Infection
    • Zoonotic fecal-oral foodborne infection
    • Associated with unpasteurized cheeses, ready-to-eat meats/foods, produce
    • Can replicate in fridge, survive in freezer
  10. Listeria Virulence Factors
    • Listeriolysin O (LLO)
    • Actin polymerization factor ActA
  11. Listeria monocytogenes Infection/Pathogenesis
    • Crosses intestinal barrier to cause invasive disseminated disease
    • Replicates inside of epithelial cells, hepatocytes, bactericidal macrophages
    • Not effected by antibody/complement responses because intracellular
  12. Listeriolysin O
    • Essential for Virulence
    • Binds to cholesterol containing membranes
    • Attaches pores through which cytoplasm can escape
    • Lyses phagosome
    • Most active at 5.5 pH
    •    -This means it is best at lysing phagosomes, not host cell membranes, keeping their environment intact
  13. ActA
    • Essential Virulence Factor for bacteria
    • Facilitates cell to cell spread
    • Uses hosts cytoskeleton
    • Similar to other intracellulars: Shigella, Ricketsia, Burkholderia
    • Used to understand host cells
  14. Listeria treatment
    • Ampicillin/Amoxacillin and Gentamycin
    • 20-30% fatality rate with treatment
  15. Listeria Outbreaks
    • 2011 (Jensen Farms Cantalope): 147 infected, 33 dead, 1 miscarriage, 60 day incubation time
    • 2012 (Frescolina Marte Brand Ricotta Salata Cheese): 20 infected, 4 dead.
  16. Listeria monocytogenes Immunity
    • Requires cellular mediated, humoral doesn't work.
    • Infection leads to long term protective immunity
    • No use for vaccine, chemotherapeutic is in making
  17. L. monocytogenes Immunotherapy
    • Immunotherapy: Utilizes body's natural immune system to fight infection
    • Use attenuated strains (deltaActA/inlB or deltaprfA+hly) to safely immunize
    • Engineer L. mono to express tumor antigens (HPV-E7/mesothelin)
    • Stimulate antigen specific T-cell response
  18. Corynebacterium diphtheriae Morphology
    • koryne-club
    • Bacterion- little rod
    • Small, Gram-positive bacilli (often irregular shape)
    • Non-motile
    • Facultative aerobe
    • Catalase +
    • Urease -
  19. Symptoms of Diphtheria
    • Respiratory:
    • Mostly in children
    • Fever/Sore throat
    • Pseudomembrane/pharynx
    •   -composed of fibrin, leukocytes, necrotic epithelial cells, and diphtheria
    • Cutaneous:
    • Minor lesions to non-healing ulcers
  20. Diphtheria Diagnosis
    • Gram + rods in throat swab
    • Black colonies on potassium tellurite agar
    • methylene blue stain in Loeffler's coagulated blood agar
  21. Diphtheria Toxin (DT)
    • Encoded by temperate beta-phage
    • Expression induced upon iron starvation
    • Is AB toxin
    •    -three subunits B/T/A: Binding, Translocation, Active
    •    -Transloction needs phagosome acidification
    • Receptor discovered through cDNA library cloning
    •     -HB-EGF heparin-binding epidermal growth factor
    • DT enters cells and ADP-ribosylates EF-2
    •     -EF-2 required for protein synthesis
    •     -Uniquely modified histidine in EF-2 called diphthamide is target of DT
    •     -Inhibition causes cell death
  22. Diphtheria History
    • Killed 80% of children under ten in early colonies
    • In 1920s, 200,000 cases/13-15,000 deaths
    • Worldwide Today: 30,000 cases/3,000 dead
  23. Diphtheria Treatment
    • Antitoxin: Neutralizes toxin (antibodies)
    • Penicillin/Erythromycin: eliminate colonizing bacteria, prevent additional secretion
    • DPT Vaccine: ensure long term protective immunity, infection does not always cause immunity
  24. Diphtheria Vaccine History
    • 1890-antitoxin treatment by Emil von Behring (horse/guinea pig)(first nobel prize in med.)
    • 1894-Early use of antitoxin (horse) in US
    • 1914: William Park shows combo antitoxin/toxin can confer immunity
    • 1923: Gaston Ramon/Alexander Glenny develop DT toxoid using heat/formalin.
    • 1964: Adjuvant added to the DTP vaccine
    • 2003: last documented case of Diphtheria in US
  25. Current Diphtheria Vaccines in US
    • DTap: Diphtheria, Tetanus, acellular Pertussis
    • DT: Diphtheria, Tetanus
    • Tdap: Tetanus, diptheria, acellular pertussis
    • Td: Tentanus, diphtheria
  26. Important Factoids
    • Listeria monocytogenes is an important foodborne pathogen that primarily affects pregnant women and still causes outbreaks in
    • the US
    • L. monocytogenes requires Listeriolysin O and ActA to cause disease

    L. monocytogenes is being developed as an immunotherapeutic tool


    • Corynebacterium diphtheriae causes
    • the disease Diphtheria through the activation of cell death by circulating Diphtheria toxin

    Diphtheria Toxin works by inhibiting protein synthesis in host cells through the ADP ribosylation of EF-2



    Inactivated Diphtheria Toxin is a highly effective vaccine that has eradicated Diphtheria in the US since 2003

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