Micro Exam 3- part 5

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hansen419
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302130
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Micro Exam 3- part 5
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2015-05-04 22:36:44
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Microbiology
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Micro Exam 3- part 5
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  1. What are the common normal flora found in the large and small intestines?
    • Bacteroides
    • Clostridium
    • Enterococcus
    • Enterobacteriaceae
    • Lactobacillus
    • Peptostreptococcus
    • Staphylococcus
  2. Helicobacter pylori- gram and shape?
    Curved gram negative rod
  3. What are the virulence mechanisms associated with H. pylori?
    • Motile (flagella)
    • Adhesins
    • Urease (neutralizes stomach acid)
    • vacA (encodes for a cytotoxin- induces vacuoles)
    • cagA (cytotoxin associated gene, increase virulence)¬†
    • Induce inflammation
  4. Which two diseases is H. pylori implicated in?
    • Chronic gastritis
    • Gastric and duodenal ulcers
  5. How is EPEC transmitted?
    Contaminated food and water
  6. What are the virulence mechanisms of EPEC?
    • -Attachment via bundle-forming pili
    • -Type III secretion system
    • -Intimate contact with enterocyte via intimin
    • -Actin recruitment via activated tyrosine kinase
    • -Deformation of microvilli and pedestal formation
  7. How is EPEC diagnosed in the lab?
    Lactose positive on MacConkey Agar
  8. How is Shigella often transmitted?
    • Oral-fecal route
    • Contaminated water or food
  9. Shigella- gram and shape?
    Gram negative bacilli
  10. Which serogroup of Shigella causes the most infections in the U.S.?
    S. sonnei (Group D)
  11. What are the virulence mechanisms of Shigella?
    • -Invasion- type II secretion system
    • -Toxin production (S. dysenteriae)
    • -Attaches to enterocyte or M cell
    • -Taken up by the cell, transcytoses through the cell, phagocytosed by macrophages
    • -Macrophages release IL-1 and IL-8, causes influx of PMNs and inflammation
    • -Intracellular spread via actin rearrangement
  12. How is Shigella diagnosed in the lab?
    Lactose negative
  13. What is the clinical manifestation of Shigella?
    Baillary dysentery
  14. Which bacteria produce Shiga toxin?
    E coli O157:H7 and Shigella dysenteriae
  15. How is EHEC transmitted?
    • Contaminated food or water (usually beef)
    • Person to person (oral-fecal)
  16. What are the O and H indicative of in E. coli O157:H7?
    • O= antigen serotype
    • H= flagellar serotype
  17. What is the mechanism of action of the Shiga toxin (or Shiga-like toxin)?
    • AB toxin
    • -Binds to Gb3 receptor on host cell (highest concentration in renal tissue)
    • -Cleaves 28s ribosome
    • -Prevents protein synthesis
  18. What are the clinical manifestations of EHEC?
    • Diarrhea
    • Hemolytic Uremic Syndome (acute renal failure, thrombocytopenia, hemoyltic anemia)
  19. What are the culture characteristics of EHEC?
    • Lactose positive¬†
    • Sorbitol negative
  20. Vibrio cholerae- gram and shape?
    Curved gram negative bacilli
  21. What is a serogroup?
    Same species with different antigenic determinants on cell surface
  22. What is a biotype?
    Same species with different physiological or biochemical traits
  23. What is the virulence mechanism of V. cholerae?
    • Cholera toxin
    • -AB toin
    • -A subunit ADP riboslates Gs protein--> increase levels of cAMP --> activate CFTR --> efflux of ions and water

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