Lecture 5 - Virulence factors, toxins Flashcards Preview

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Flashcards in Lecture 5 - Virulence factors, toxins Deck (18):
0

What is a virulence factor

anything that enhances the ability of microbes to cause disease

1

6 major examples of virulence factors

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

2

Define a bacterial toxin

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

3

Gram negative bacteria have what type of toxins?

Endotoxins (ALL)
Exotoxins (often have one or two)

4

Gram positive bacteria have what toxins?

Exotoxins
NO ENDOTOXINS

5

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

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

6

What is the LPS binding protein

TLR-4

7

What does the TLR-4 -LPS binding stimulate

activates many inflammatory cells including macrophages

8

LPS-activated monocytes/macrophages produce what?

Cytokines such as IL-1 and TNF-alpha

9

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

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

10

LPS itself activates:

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

11

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

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

12

3 major types of exotoxins as classified by function

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

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Role of Cytolytic toxins

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

14

How does an A-B toxin work

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

15

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

True

16

What is the function of Superantigens

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

17

4 important A-B exotoxins and their actions

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