Lecture 1 - Pathogens

Question 1

What are the 5 stages of pathogenesis?

Answer 1

Transmission
Infection
Establishment
Persist
Disease

Question 2

Give an example of where site of entry is important.

Answer 2

Staph aureus in the mouth is useless but if it moves to the blood is very dangerous

Question 3

What is LD50?

Answer 3

Dosage required for 50% mortality rate

Question 4

What are 3 host facotrs that affect pathogenesis?

Answer 4

immune status
prior exposure
genetic predisposition

Question 5

What are Koch’s postulates? (wrong)

Answer 5

Organism must not be healthy
Must be able to grow in pure culture
Should cause disease in other organisms
Must be able to be reisolated

Question 6

What is the problem with Koch’s 4th postulate?

Give an example

Answer 6

• Cant culture some (nutrition, O2 req, sensitivity)

- Catscratch disease - can only visualise not grow

Question 7

What was the experiment done to do with the microbiota?

Answer 7

• Took microbiota from obese and healthy twin
• Put into mice
• Obese microbiota mouse had increased fat

Question 8

What is the problem with antibiotics and give an example?

Answer 8

• Kills the microbiota

- Clostridium difficile then proliferates and causes diarrhea

Question 9

What are the 3 types of pathogens?

Answer 9

Overt/strict
Opportunistic
Facultive

Question 10

What is an overt/strict pathogen and give an example

Answer 10

Only human diease

Neisseria gonorrhaeae

Question 11

What is an opportunistic pathogen and give an example

Answer 11

Normal flora that then turns bad

Pseudomonas aeuriginosa

Question 12

What is a facultive pathogen and give an example

Answer 12

Doesnt want to be a pathogen but can cause disease

Bacillus anthracia

Question 13

What are the strategies pathogens use to infect?

Answer 13

Extracellular
Local toxin producing
Intracellular

Question 14

What are examples of general virulence factor functions and the structures involved

Answer 14

Attachment and entry - adhesins
Spread - flagella
Multiplication
Evasion - capsule
Shedding damage

Question 15

What are the two types of toxin?

Answer 15

Endotoxin, exotoxin

Question 16

What are the features of endotoxins?

Answer 16

Cell bound and heat stable

Question 17

What are the features of exotoxins?

Answer 17

Released extracellularly, heat labile, specific targets, highly toxic

Question 18

What is an enterotoxin?

Answer 18

Exotoxin that acts in the small intestine

Question 19

What is a toxoid?

Answer 19

Inactivated toxin used as a vaccine

Question 20

Features of Botulinum toxin

Answer 20

• Neurotoxin that blocks ACh in synapse

- 1ng can kill 1 million guinea pigs (1/50 grain of salt)

Question 21

Give an example of a bacteria that produces a toxin and what are its features?

Answer 21

Vibrio cholerae
gr-
Transmission in water orally
Colonises small intestine

Question 22

What does the cholera toxin do?

Answer 22

Increases AC activity leading to increases cAMP

This changes Na/Cl flux in cells causing a massive loss of fluid (diarrhea)

Question 23

What is interesting about the gene for the Cholera toxin?

Answer 23

Its part of a lysogenic phage

Question 24

What is the TCP?

Answer 24

Toxin co-regulated pilus is a receptor for the phage and is required for colonisation of Cholera

Question 25

What did Waldar and Mekalonos do?

Answer 25

Looked at transduction efficiency between two strains of Cholera, one with TCP and one with out

Question 26

What are 3 methods for finding genes involved in infection?

Answer 26

Differential fluorescence induction
Random mutagenesis
Signature tagged mutagenesis

Question 27

What is differential fluorescence induction?

Answer 27

Take many strains with seperate promoter to drive GFP and simulated different stages of infection - look for active promoters