Lecture 5 - Virulence factors, toxins

Question 0

6 major examples of virulence factors

Answer 0

1. Transmissibility (Acid resistance)
2. Adherence (Colonization)
3. Invasiveness (Collagenase, Hyaluronidase)
4. Evade Immunity (Capsule)
5. Damage Mechanism (Endotoxins, Exotoxins, etc.)
6. Antibiotic Resistance

Question 1

What is a virulence factor

Answer 1

anything that enhances the ability of microbes to cause disease

Question 2

Define a bacterial toxin

Answer 2

Bacterial components or products that directly harm tissue or trigger destructive biologic activities

Question 3

Gram negative bacteria have what type of toxins?

Answer 3

Endotoxins (ALL)

Exotoxins (often have one or two)

Question 4

Gram positive bacteria have what toxins?

Answer 4

Exotoxins

NO ENDOTOXINS

Question 5

T or F, Endotoxins are produced and secreted from a Gram Positive cell.

Answer 5

False, Exotoxins are produced and secreted from a Gram positive cell

Question 6

What is the LPS binding protein

Answer 6

TLR-4

Question 7

What does the TLR-4 -LPS binding stimulate

Answer 7

activates many inflammatory cells including macrophages

Question 8

LPS-activated monocytes/macrophages produce what?

Answer 8

Cytokines such as IL-1 and TNF-alpha

Question 9

How is Nitric Oxide produced and what is its role in inflammation

Answer 9

TNF-alpha stimulates endothelium to produce NO and that causes precapillary sphincters to relax

Question 10

LPS itself activates:

Answer 10

1. Complement cascade (which initiates inflammation)
2. Hageman factor
3. Platelets
4. Macrophages/Monocytes
   * This is helpful when small amounts of G - come through we don’t have to wait for adaptive immune system

Question 11

Large numbers of gram negative bacteria may cause sepsis and what 2 responses:

Answer 11

1. Hypovolemic Shock (Cardiovascular failure)
2. Disseminated Intravascular Coagulation
   
   • Multiple Organ shutdown
   • Acute Respiratory Distress Syndrome often occurs

Question 12

3 major types of exotoxins as classified by function

Answer 12

1. Cytolytic toxins
2. A-B toxins
3. Superantigens

Question 13

Role of Cytolytic toxins

Answer 13

Disrupt cell membranes by either 1) forming pores in membrane or 2)Cleaving the charged groups of the phospholipids of the membrane

Question 14

How does an A-B toxin work

Answer 14

The B protein component binds specifically to certain cells. After toxin attachment, the A unit enters the cell as an enzyme

Question 15

T or F, A-B toxins are the most toxic materials known

Answer 15

True

Question 16

What is the function of Superantigens

Answer 16

Inappropriately bind the Th cell TCR to HLA class II molecule on APC. This initiates Th cell/macrophage activation, and a hugely excessive cytokine production

Question 17

4 important A-B exotoxins and their actions

Answer 17

1. Toxin blocks protein elongation factor
2. Toxin blocks a G-protein, ionic imbalance and water loss
3. Toxin cuts host ribosomal RNA resulting in inhibition of protein synthesis
4. Toxin blocks vesicle fusion and release of neurotransmitters