Lecture 14- Exotoxins and Exoenzymes

Question 1

What are the two general effects that exotoxins may have?

Answer 1

Stopping cells from function normally (as with shiga-like toxins)
Modify cellular activities (as in cholera)

Question 2

Is microbial presence required for delivery of toxins?

Answer 2

No, toxins may ingested on there own as is the case with staphylococcal food poisoning

Question 3

What is toxic shock syndrome toxin?

Answer 3

Small toxin, which acts extracellularly as a super antigen

Question 4

What symptoms are produced as a result of toxic shock syndrome?

Answer 4

Shock (life threatening condition caused by a failure of the body to meet its oxygen demands)
Fever
Reduced blood volume/pressure
Leaky vasculature, vasodilation
desquamation
diarrhoea
vomiting

Question 5

What toxin acts in cholera?

Answer 5

Multimeric AB5 protein which acts intracellularly
B unit provides entry into host cell
A subunit causes the chloride secretion and resulting diarhoea

Question 6

How does the cholera toxin have its affect?

Answer 6

It permanently activates adenylate cyclase resulting in over production of cAMP which results in release of Cl- into the lumen causing the osmotic imbalance leading to diarrhoea

Question 7

What are the consequences of developing diarrhoea?

Answer 7

There is large amounts of fluid loss and potentially loss of blood volume and shock
This is why treatment is simply fluid replacement

Question 8

What is the process of cholera infection?

Answer 8

Colonises the intestine after infected water is consumed, flagellae swim to the intestinal wall and pili provide attachment, the nutrients available in the gut allow the growth of the bacteria

Question 9

What is the function of the degradative enzymes released by some bacteria?

Answer 9

Allow deeper penetration into tissues, release of nutrients and destruction of immune cells

Question 10

What occurs in a burn when there is a pseudomonas aeruginosa infection?

Answer 10

Pseudomonas acts as an opportunistic pathogen taking advantage of the compromised immune system.
Colonisation occurs via flagellae and pili
Toxins are released by the bacteria causing tissue necrosis
Enzymes are used to promote bacterial spread allowing the bacteria to cause septicaemia by entry into the blood

Question 11

What is the most important enzyme in a pseudomonas aeruginosa infection?

Answer 11

Elastases which degrade collagen, elastin and other host proteins including IgG, Complement and chemokines

Question 12

What are the two elastases which act synergistically in a P.Aeruginosa infection?

Answer 12

Las A which is a serin protease that nicks the proteins

Las B which is a zinc metalloprotease which fully degrades nicked proteins