3C - Exotoxins and Endotoxins

Question 1

Infectious Disease Process

Answer 1

◦ Enter host
◦ Multiply
◦ Evade host defenses
◦ Harm host

Question 2

Endotoxins or lipopolysaccharides

Answer 2

only associated with gram-negative bacteria- damage to cells is usually secondary to the activation of complement and the inflammatory cascade

Question 3

Exotoxins

Answer 3

are produced by both gram-positive and gram-negative bacteria and may directly kill or damage cells
‣ Exotoxins are grouped according to their effect on certain cells and tissues
• Leukotoxins
• Neurotoxins
• Enterotoxins

Question 4

Exotoxins function

Answer 4

‣ Released as the bacteria live, divide and grow in numbers ‣ Travel from the site of infection to distant sites.
‣ Cytotoxic causing direct cytolysis (Staph aureus)
‣ Enterotoxic and use the A-B system
‣ Neurotoxic such Clostridium botulinum, and C. tetani

Question 5

Cytotoxins

Answer 5

‣ Alpha toxin from Staphylococcus Aureus forms a pore in the cell membrane causing the cell to die
‣ Harms immune cells

Question 6

Tetanus Toxin

Answer 6

type of neurotoxin
from Clostridium tetani blocks the release of glycine (glycine inhibits the release of ACH) so muscles can’t relax → lock jaw and tetanus
• Muscles can’t stop contracting

Question 7

Botulinum toxin

Answer 7

type of neurotoxin
from Clostridium botulinum block acetylcholine receptors- flaccid paralysis
• Muscles can’t contract

Question 8

Enterotoxin AB system

Answer 8

‣ Vibrio Cholerae causes cholera
‣ B- binds to the cell membrane and facilitates entry of the “A” part of the toxin into the cell
‣ A- causes loss of sodium and therefore water from the cell
• B- is the guy that can pick locks
• A- is the bad guy

Question 9

Exotoxic shock

Answer 9

occurs when large quantities of endotoxin are released into the circulatory system
• → Release of pro-inflammatory cytokines from macrophages and endothelial cells (cells that line the blood vessels)
• → Activation of complement with release of endogenous pyrogens from the host cells
• → Activates the coagulation cascade

Question 10

Lipopolysaccharide (LPS)

Answer 10

one of the most powerful immune stimuli known and activates almost every immune mechanism, as well as the clotting pathway

Question 11

DIC

Answer 11

Disseminated intravascular coagulation

Question 12

Lipoteichoic acid

Answer 12

superantigens - stimulate large numbers of immune cells → huge inflammatory response → tissue damage and activation of complement
rom gram positive bacteria like Staphylococcus aureus behaves like endotoxin and mimics LPS

Question 13

damage of exotoxins

Answer 13

• Exotoxins – do the damage the cells but an immune response can neutralize the toxin.
◦ for example Tetanus toxoid makes an excellent vaccine

Question 14

damage of endotoxins

Answer 14

• Endotoxins- the immune system does the damage, but the immune response is unablento neutralize the toxin.
◦ Endotoxins don’t make good vaccines