10.2- Introduction to Virulence

Question 1

Define virulence factors

Answer 1

The way that microbes overcome our defenses.
- Features that help microbes adhere to host cells, invade host tissues, acquire nutrients, and evade immune defenses. Toxins are also included.
Classic factors: pathogen toxicity, aggressiveness, and transmission.

Question 2

What are virulence factors of toxins?

Answer 2

Lipopolysaccharides (LPS) in gram-negative

Diverse Secreted toxins

Question 3

What are virulence factors of immune system evasion features?

Answer 3

Diverse enzymes
Various toxins
Capsules

Question 4

What are virulence factors that effect invasion?

Answer 4

Flagella
Various toxins
Enzymes (kinases, coagulases, etc.)

Question 5

What are nutrient acquisition virulence factors?

Answer 5

Diverse enzymes

Iron binding proteins

Question 6

What are adhesion virulence factors?

Answer 6

Fimbrae

Binding factors

Question 7

What is the difference between virulent and attenuated pathogens?

Answer 7

Attenuated pathogens don’t cause disease in a competent host as they have lost their virulence factors. This happens if they are grown in a petri dish where they are not exposed to environmental factors, and also occurs when pathogens are not exposed to certain environmental factors (like a specific antibiotic) for a long period of time.

Question 8

What does ID50 mean?

Answer 8

Infectious dose 50
This describes how many cells (bacterial, fungal, or parasitic) are needed to establish an infection in 50% of exposed susceptible hosts.

Question 9

Define LD50

Answer 9

Describes the amount of toxin required to kill 50% of affected hosts that are not treated.

Question 10

Define mortality rate

Answer 10

The legality of an infectious agent.

Question 11

Define toxins

Answer 11

Molecules that generate a number of adverse affects such as tissue damage and suppressed immune response.

Question 12

Define toxogenic

Answer 12

Used to describe microbes that produce toxins.

Question 13

Define toxemia

Answer 13

When toxins enter the blood stream and are spread throughout the body.

Question 14

What type of microbe makes most types of toxins seen in clinical scenarios?

Answer 14

Bacteria

Question 15

What are the seven properties of endotoxins?

Answer 15

Made of: Lipids
Made by: Gram-negative bacteria
Released from: Gram-negative cell wall when bacteria divide or die.
Vaccines: No
Fever: Yes
Can be neutralized in patient: No
Toxicity level: Low (relatively high LD50)

Question 16

What are the seven properties of exotoxins?

Answer 16

Made of: Proteins
Made by: Gram negative and positive bacteria
Released from: Actively growing bacteria
Vaccines: Yes (some)
Fever: Sometimes (certain superantigens)
Can be neutralized in patient: Yes (some)
Toxicity level: High (many have low LD50)

Question 17

When do gram negative bacteria release most of their endotoxins?

Answer 17

When they die, but a small amount is released when they divide.

Question 18

Do gram positive bacteria make endotoxins?

Answer 18

No

Question 19

What is type I exotoxin’s mode of action?

Answer 19

Bind to target host cells using receptors on their surface. By binding to the receptors they do, they propagate a signal cascade the can alter gene expression.
I.E. Superantigens- stimulate an over-reaction of the immune response and can cause massive inflammation.

Question 20

What is type II exotoxin’s mode of action?

Answer 20

Membrane damaging toxins effect the host cell plasma membrane by forming pores or removing phosphate head groups from the phospholipids of the lipid membrane. This destabilizes the membrane and causes cell lysis.

Question 21

What is type III exotoxin’s mode of action?

Answer 21

They bind to a receptor and then enter the cell to exert effects.

Question 22

Define solubility

Answer 22

Describes a substances ability to dissolve in a solvent, especially water.