17 - Host/Microbe Interactions

  1. What are the 3 symbiotic relationships between host and microbe?
    • Mutualism - Both benefit
    • Commensalism - One benefits, other is unharmed
    • Parasitism - One benefits at expense of host
  2. How does our normal microbiota play help us?
    • Protects us from harmful organisms by covering binding sites, consuming available nutrients and producing toxic compounds, and stimulating our immune systems.
    • Acquired at birth.
  3. 3 Things that can kill normal microbiota:
    • 1. Chemicals/Chemo
    • 2. Burns
    • 3. Auto-immune Defeciencies
  4. When is the term "infection" used?
    • If the colonizing organism has a parasitic relationship with the host.
    • An infection that results in disease is termed an "infections disease."
  5. What are signs and symptoms?
    • Symptoms - Experienced by patient, ie pain/nausea
    • Signs - Can be observed through examination, ie Rash, Swelling, Pus
  6. What are primary and secondary infections?
    • Primary - Initial infection
    • Secondary - Additional infections resulting from the primary infection
  7. What is pathogenicity?
    The ability of a pathogen to produce an infectious disease in an organism.
  8. What is virulence?
    • Term referring to a pathogens disease causing ability.
    • Highly virulent organisms have a high degree of pathogenicity.
  9. What is an opportunistic pathogen?
    Microbes that cause disease when the body's defenses are down.
  10. What is the "infectious dose?"
    • Number of organisms required to establish infection
    • Diseases with SMALL infectious doses are more easily spread than diseases with HIGH infectious doses because less of the microbe is needed.
  11. What is the course of an infectious disease?
    • Incubation - Time between infection and onset of symptoms
    • Illness - Signs and symptoms
    • Convalescence - Recuperation and recovery; may still be contagious
  12. What are the duration of symptoms?
    • Acute - Rapid onset, last a short time
    • Chronic - Develop slowly and persist
    • Latent - Never completely eliminated, may be reactive
  13. What is a localized infection?
    • Limited to a small area.
    • Example - Boil
  14. What is a systemic or generalized infection?
    • Microbe spreads throughout body
    • Example - Measles
  15. What is toxemia?
    Toxins circulating in the blood stream
  16. What is viremia?
    Viruses cirulating in the blood stream
  17. What is septicemia?
    Life-threatening illness caused by infectious agent or its products circulating in the blood
  18. What separates disease and non-disease causing organisms?
    Their ability to overcome the body's immune system
  19. What is a "mechanism of pathogenicity?"
    • Mechanism used to overcome the body's immune responses
    • More than one mechanism is called "Virulence Determinants"
  20. What steps must an organism take to cause disease?
    • Adherence - Binding to the hosts cells
    • Colonization - Must successfully multiply, compete for nutrients
    • Delivery of Effector Molecules - Must be able to deliver colonized cells to host
  21. How do organisms get in to our bodies?
    • Penetration of skin - most difficult
    • Penetration of mucous membranes - most common
  22. How do bacteria avoid the hosts defenses?
    • Hide in a host cell - some can transfer from cell to cell
    • Avoid being killed by complement protiens - Gram negative cells more susceptible
    • Avoiding antibodies -
  23. How can a bacteria avoid antibodies?
    • IgA protease
    • Antigenic Variation - alternation of surface antigens
    • Mimicking Host Molecules
  24. What are exotoxins?
    • Toxins that are leaked or secreted by bacterium
    • Among most potent toxins known
    • Can act locally or systemically
  25. What are the 3 types of toxins?
    • Neurotoxins - damage nervous system
    • Enterotoxins - damage intestines/digestive tract
    • Cytotoxins - Damage to variety of cells, cause interference with cell function and lysis
  26. What are membrane damaging toxins?
    Disrupt the plasma membrane of a cell
  27. What are superantigens?
    Antigens that override T-Cell response and cause toxis effects due to massive release of cytokines by helper t-cells.

    Example: TSS
  28. Which toxin in responsible for Septic Shock?
  29. What are some damaging effects of immune response?
    • Fever
    • Drop in blood pressure
    • Inflammation
  30. What are the mechanisms of viral pathogenesis?
    • Binding to host cell/Invasion
    • Avoiding immune responses
  31. What are the mechanisms of Eukaryotic Pathogenesis?
    • Fungi - Infection begins with inhalation of airborne particles, Spores lodge in lung tissues
    • Eukaryotic Parasites - Most live in intestinal tract, or enter body via bite of an arthropod, attach to hosts via specialized receptors, some hide within host cells.
Card Set
17 - Host/Microbe Interactions
17 - Host Microbe Interactions