15 - Pathogenicity

Question 1

What are some ways microbes enter the body?

Answer 1

1. mucous membranes
2. skin

Question 2

What is the most common way microbes enter the body?

Answer 2

respiratory tract

Question 3

What is the second most common way microbes enter the body?

Answer 3

gastrointestinal tract

Question 4

What is the ID50?

Answer 4

dose of microbe that is infectious for 50% of the population

Question 5

What are four ways that microbes evade the host immune response?

Answer 5

1. capsules (resist immune defense)
2. cell wall (certain proteins/lipids resist immune response)
3. enzymes
4. antigenic variation

Question 6

Antigenic variation

Answer 6

surface antigens become unaffected by antibodies

Question 7

How can bacteria damage host cells?

Answer 7

use of host’s nutrients and direct damage (cell lysis/nutrient use/produce waste)

Question 8

Endotoxin

Answer 8

• toxins composed of lips that are part of the cell membrane
• outer portion of cell wall in Gram - LPS (lipid A is endotoxin) released when gram - bacteria die (cell walls lysed)
• all endotoxins produce same symptoms
• cause macrophages to release high level of cytokines

Question 9

Exotoxin

Answer 9

• toxic substances released outside the cell
• mostly gram +
• destroy host cell or inhibit metabolic functions
• disease is generally caused by exotoxin and not bacteria
• 3 different types

Question 10

What are the 3 types of exotoxins?

Answer 10

1. A-B toxins
2. Membrane-disrupting toxins
3. Superantigens

Question 11

What do A-B toxins do?

Answer 11

most common exotoxins - A-enzyme component, B-binding component

Question 12

A-B toxin examples

Answer 12

1. diphtheria toxin
2. botulinum toxin
3. tetanus toxin
4. vibrio enterotoxin

Question 13

Membrane-disrupting toxin function

Answer 13

form protein channels, and disrupt phospholipid portion/lyse host cells

Question 14

Example of membrane-disrupting toxin

Answer 14

gas gangrene toxin

Question 15

Superantigens function

Answer 15

bacteria proteins, provoke intense immune response

Question 16

Superantigens example

Answer 16

1. Streptococcus pyogenes
2. Staphylococcal enterotoxin

Question 17

What are some examples of endotoxins?

Answer 17

1. Salmonella typhi
2. Neisseria meningitis

Question 18

What can happen when you take antibiotics for a gram-negative infection, why?

Answer 18

The cell death from the antibiotics releases endotoxin and worsens the symptoms until the toxin is degraded.

Question 19

What 7 ways can viruses damage host cells?

Answer 19

1. stop host cell macromolecule synthesis
2. destruction of intracellular contents
3. inclusion bodies (granules contain viral parts)
4. fuse adjacent cells
5. changes in function, reduce cytokine production
6. changes in surface antigens of host, target for destruction
7. cancer

Question 20

How do microbes exit the body (4)?

Answer 20

1. mucous membranes
2. skin or wounds
   - generally the same as endry

Question 21

Endotoxic chock

Answer 21

macrophages release TNF, increase blood capillary permeability, lose fluid, drop in blood pressure