chapter 27-5

Question 1

Exotoxins

Answer 1

Proteins released from the pathogen cell as it grows.
Three categories:
-Cytolytic toxins
-AB toxins
-Superantigen toxins
—Toxins that cause extreme immune reactions.

Question 2

Cytolytic toxins

Answer 2

Work by degrading cytoplasmic membrane integrity, causing cell lysis and death.
–Toxins that lyse red blood cells are called hemolysins.

Question 3

AB toxins

Answer 3

Consist of two subunits, A and B.
Work by binding to host receptor (B) and transferring damaging agent (A) across the cell membrane.
–Ex. diptheria toxin , tetanus toxin, botulism toxin.

Question 4

Diptheria toxin, Tetanus toxin and botulism toxin.

Answer 4

Diptheria: Protein synthesis stops.
Botulism: blocks release of A, inhibiting contraction.
Tetanus: Binds to inhibitory interneurons, preventing release of glycine and relaxation of muscle.

Question 5

Enterotoxins

Answer 5

Exotoxins whose activity affects small intestine.
Generally cause massive secretion of fluid into intestinal lumen, resulting in vomiting and diarrhea.
-cholera toxin.

Question 6

Endotoxins

Answer 6

Lipopolysaccharide portion of cell envelope of certain Gram - bacteria, which can act as a toxin.
Generally less toxic than exotoxins.

Question 7

Host risk factors for infection

Answer 7

Compromised host:

• One or more resistance mechanisms are inactive.
• The probability of infection is increased.
• Age is an important factor
• –Very young and very old individuals are more susceptible.
• Stress can predispose a healthy individual to disease.
• Diet plays a role in host susceptibility to infection.
• Certain genetic conditions can compromise a host.

Question 8

Innate resistance to infection

Answer 8

Hosts have innate resistance to most pathogens

• natural host resistance
• tissue specificity
• physical and chemical barriers

Question 9

Defense summary

Answer 9

End of 27 slide.