MMI 301-Exam 2-Lecture 8: Microbes as Pathogens

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MMI 301-Exam 2-Lecture 8: Microbes as Pathogens
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2013-10-25 12:21:04
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MMI 301-Exam 2
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  1. Normal Biota and Benefits
    Bacteria that already live in body, protect from colonization, provide nutrition and stimulate immune system
  2. Pathogenic Bacteria
    Virulent Bacteria that commonly cause disease
  3. Opportunistic Pathogens
    Bacteria that will cause disease w/ pre-existing conditions
  4. Acute Disease
    Rapid Onset, Rapid resolution  (cholera)
  5. Chronic Disease
    Slow onset, slow resolution (tuberculosis)
  6. Recurrent Disease
    Multiple acute bouts (UT E. Coli)
  7. Pyogenic Disease
    Causes fever, white cell infiltration and pus (Staph/Strep wounds)
  8. Immune-mediated Disease
    Antibody/Cellular response to organism damaged tissues (rheumatic fever)
  9. Species that enter through ingestion:
    Salmonella,Shigella, Vibrio cholerae, Listeria, Bacillus anthracis
  10. Species that enter through Inhalation
    Mycobacterium tuberculosis, Legionella pneumophila, Bordetella, B. anthracis, Staphylococcus
  11. Species that enter through Trauma
    • Clostridia tetani, B. anthracis,
    • Staphylococcus
  12. Species that enter through Arthropod Bites
    Rickettsia,Yersinia pestis, Borrelia sp.
  13. Sexually Transmitted species
    Chlamydia trachomatis, Haemophilus ducreyi, Treponema pallidum, Neisseria gonorrhoeae
  14. Species that are spread Transplacentaly
    T.pallidum, Listeria monocytogenes
  15. Species that spread through eyes
    C.trachomatis, N. gonorrhoeae, Pseudomonas, Haemophilus influenzae
  16. Bacterial Virulence Factors
    • Adhesion
    • Cellular Invasion
    • Exotoxins
    • Endotoxins
    • Superantigens
    • Capsules
    • Evasion of Immune Defenses
    • Iron Acquisition
    • Disruption of cell signalling
    • Motility
  17. Falkow's Postulates
  18. -Phenotype/property under investigation
    • should be associated with pathogenic members of a genus
    • -Specific mutagenesis of gene(s)
    • associated with the suspected virulence factors should show a measurable loss
    • of virulence in an appropriate model system. (In-frame/point mutation best)
    • -Complementation of mutatation by
    • recombinant plasmid or allelic replacement with wild type should lead to
    • restoration of pathogenicity
  19. Virulence: Sources of Adhesion
    • -Pili/fimbriae:attach to host or other bacteria
    • -Non-fimbrial surface proteins
    • -Capsule
    • -Lipoteichoic acids
    • -Flagella
  20. Process of Phagocytosis
    • -Bacteria bind cell surface
    • -Induce engulfment into a phagosome
    • -Normally phagosome acidified and it fuses with lysozyme, kill bacteria
    •          -Uses destructive enzymes and oxide   radicals
  21. Virulence: Cellular Invasion Modes
    • -Invasion with replication in cytoplasm (Rickettsiae/Shigella/Listeria)
    • -Invasion with replication in late endosomes (Salmonella)
    • -Invasion with replication in phagolysosomes (Coxiella/Mycobacteria)
    • -Special parasite vesicle: inclusion bodies of Chlamydia sp.
  22. Virulence: Spreading from cell to cell
    • -Some intracellulars can do this without ever being in extracellular environment
    • -Shigella/Listeria
    • -Enter host cells
    • -Rapidly lyse phagosome
    • -Replicate and organize polymerization of actin filaments
    • -Use actin to propel themselves into neighboring cells
    • -Lyse double membrane surrounding them
    • -Repeat
  23. Virulence: Bacterial Exotoxins: AB subunit Model
    • -Usually function as two discrete proteins subunits/two units of same protein
    • -Ability to recognize/bind specific host cell receptors from one subunit
    • -Toxic actions from other subunit
    • -Discrete elements needed for secretion from bacterial cell
    • -Also need parts for translocation across plasma membrane of host cells
    • -This depends on mode of entry
  24. Virulence Factors: Cytolytic Toxins (Hemolysins)
    • -Creation of membrane pore
    •        -alpha toxin of Staph. Aureus
    • -Enzymatic destruction of phospholipid bilyar
    •        -alpha phospholipase C of Clostridium perfringens
    • -Surfactant
    •        -delta toxin of S. aureus
  25. Virulence: Type 3 Secretion Systems
    • -Some Gram –
    • -Directly deliver bacterial proteins into host cell cytoplasm
    • -Proteins can affect a variety of different host cell functions
    •        -Cytoskeletal structure
    •        -Structure of messenger pathways
    • -Needle like structure, injects
    • -Helps E. coli make actin pedestals
  26. Sec-dependent vrs. Sec-independent
    • Type V/II: Sec-dependent
    • Typer I/III/IV: Sec-independent

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