Microbial pathogenicity

Question 1

What would happen if a person had not immune system/ a weak one?

Answer 1

• Lot’s of microbes would grow
• They would use the body as food
• The weaker the immune system, the more opportunity for microbes to infect

Question 2

What is an example of a virus?

Answer 2

H1N1 Influenza
- A single stranded RNA, enveloped virus
HIV virus –> causes AIDS disease

Question 3

How does influenzas envelope cause the need of new vaccines?

Answer 3

They are coated with a range of different proteins, that constantly change due to mix and match of RNA

• Different receptors means different areas of the body it can infect
• Therefore, new vaccines are needed

Question 4

What is an example of fungi?

Answer 4

Trichophyton spp (causes ringworm)

Question 5

What is an example of prions?

Answer 5

Kuru (laughing disease)

Question 6

What are prions?

Answer 6

Misfolded proteins

- A normal protein and a misfolded protein interacts and causes it to turn into a misfolded protein

Question 7

What is an example of a protozoa?

Answer 7

Plasmodium spp (malaria parasites)

Question 8

What is an example of Helminths?

Answer 8

Ancylostoma duodenale (hookworm)

Question 9

What is an example of a bacteria?

Answer 9

Bacillus anthracis

• Gram positive
• Endospore fomring
• Rod shaped

Question 10

What is an endospore?

Answer 10

A dormant form of bacteria

• Forms an endospore when its in bad conditions
• kills off its vegetative state to from endospore
• Can live for a long time in this form under bad conditions

Question 11

What are gram positive bacteria?

Answer 11

• Have thick cell walls that consist primarily of peptidoglycan
• Peptidoglycan traps and retains crystal violet stain
• Have plasma membrane

Question 12

What are gram negative bacteria?

Answer 12

• Do not retain the stain, crystal violet is easily rinsed away
• Have cell walls with two layers, a thin peptidoglycan layer and a thick out membrane that contains polysaccharides bonded to lipids
• Have a plasma membrane

Question 13

What are Koch’s postulates?

Answer 13

Guidelines used to demonstrate that a specific pathogen causes specific disease symptoms

Question 14

What are the rules of Koch’s postulates?

Answer 14

1. The pathogen must be present in every individual with the disease
2. A sample of the microorganism taken from the diseased host can be grown in pure culture
3. A sample of the pure culture causes the same disease when injected into a healthy host
4. The microorganism can be recovered from the experimentally infected host

Question 15

What are some exceptions of Koch’s postulates?

Answer 15

1. Microbes that can’t be cultures e.g. syphilis bug (Treponema pallidum)
2. Pathogens that also can be found in health subjects e.g. Vibrio cholera

Question 16

What is an infection?

Answer 16

About how the bacteria/ virus can get into the body

Question 17

What are the 3 stages of infection?

Answer 17

1. Adherence to host cells
2. Invasion of host tissues
3. Replication within host tissues

Question 18

What is disease?

Answer 18

Causing damage to host tissues due to infection

- Toxins are also produced

Question 19

What is the bacterial virulence factor that relates to Adherence to host cells?

Answer 19

Adhesions such as fimbriae (bind to host cells e.g. Neisseria gonorrhoeae
- Hair-like projections that are very sticky

Question 20

What is the bacterial virulence factor that relates to Invasion of host tissues

Answer 20

Motility (moving through mucus) e.g. helicobacter pylori (responsible for stomach ulcers)
- Flagella

Question 21

What is the bacterial virulence factor that relates to Replication within host tissues?

Answer 21

Siderophores (bind iron) Yersinia pestis e.g. the siderophore yersiniabactin solublises metal bound to host proteins and transports it back to the bacteria

Capsules (resist phagocytosis from white blood cells) e.g. streptococcus pneumoniae
Avoids the immune system

Question 22

What is the bacterial virulence factor that relates to disease?

Answer 22

Endotoxins = cause inflammation
Exotoxins = can be fatal

Question 23

What are endotoxins?

Answer 23

Are lipopolysaccharides (LPS) components found in the outer membrane of gram-negative bacteria, and elicit strong immune responses

Question 24

What are some factors of endotoxins?

Answer 24

They are only released when the bacteria is destroyed

- Sparks inflammation when released

Question 25

How can we know what type of virulence factor the bacteria causes?

Answer 25

Gram negative and gram positive test

Question 26

What are exotoxins?

Answer 26

Are produced within living bacteria, and then released into the surrounding medium while they are still alive.

Question 27

What are the three types of exotoxins?

Answer 27

Cytotoxins, Neurotoxins and enterotoxins

Question 28

What are Cytotoxins?

Answer 28

Strepholysin which is a extracellular enzyme is produced by the bacteria such as staphylococcus pyogenes which causes the complete lysis of red blood cells (Beta hemolysis)

Question 29

What are Neurotoxins?

Answer 29

Botulinum produced by the bacteria such as Clostridium botulinum which causes paralysis

• Very deadly
• Stops neurotransmitters from being released from the axon terminal

Question 30

What are enterotoxins?

Answer 30

Shiga toxin is produced by the bacteria Shigella dysenteriae and causes severe dysentery (infectious diarrhea)
- Spreads through contaminated food and water