Lecture 1 - Pathogens Flashcards
What are the 5 stages of pathogenesis?
Transmission Infection Establishment Persist Disease
Give an example of where site of entry is important.
Staph aureus in the mouth is useless but if it moves to the blood is very dangerous
What is LD50?
Dosage required for 50% mortality rate
What are 3 host facotrs that affect pathogenesis?
immune status
prior exposure
genetic predisposition
What are Koch’s postulates? (wrong)
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
What is the problem with Koch’s 4th postulate?
Give an example
- Cant culture some (nutrition, O2 req, sensitivity)
- Catscratch disease - can only visualise not grow
What was the experiment done to do with the microbiota?
- Took microbiota from obese and healthy twin
- Put into mice
- Obese microbiota mouse had increased fat
What is the problem with antibiotics and give an example?
- Kills the microbiota
- Clostridium difficile then proliferates and causes diarrhea
What are the 3 types of pathogens?
Overt/strict
Opportunistic
Facultive
What is an overt/strict pathogen and give an example
Only human diease
Neisseria gonorrhaeae
What is an opportunistic pathogen and give an example
Normal flora that then turns bad
Pseudomonas aeuriginosa
What is a facultive pathogen and give an example
Doesnt want to be a pathogen but can cause disease
Bacillus anthracia
What are the strategies pathogens use to infect?
Extracellular
Local toxin producing
Intracellular
What are examples of general virulence factor functions and the structures involved
Attachment and entry - adhesins Spread - flagella Multiplication Evasion - capsule Shedding damage
What are the two types of toxin?
Endotoxin, exotoxin
What are the features of endotoxins?
Cell bound and heat stable
What are the features of exotoxins?
Released extracellularly, heat labile, specific targets, highly toxic
What is an enterotoxin?
Exotoxin that acts in the small intestine
What is a toxoid?
Inactivated toxin used as a vaccine
Features of Botulinum toxin
- Neurotoxin that blocks ACh in synapse
- 1ng can kill 1 million guinea pigs (1/50 grain of salt)
Give an example of a bacteria that produces a toxin and what are its features?
Vibrio cholerae
gr-
Transmission in water orally
Colonises small intestine
What does the cholera toxin do?
Increases AC activity leading to increases cAMP
This changes Na/Cl flux in cells causing a massive loss of fluid (diarrhea)
What is interesting about the gene for the Cholera toxin?
Its part of a lysogenic phage
What is the TCP?
Toxin co-regulated pilus is a receptor for the phage and is required for colonisation of Cholera
What did Waldar and Mekalonos do?
Looked at transduction efficiency between two strains of Cholera, one with TCP and one with out
What are 3 methods for finding genes involved in infection?
Differential fluorescence induction
Random mutagenesis
Signature tagged mutagenesis
What is differential fluorescence induction?
Take many strains with seperate promoter to drive GFP and simulated different stages of infection - look for active promoters
