Pathogens - Intro Flashcards
Define Pathogen?
An organism which can cause disease
Define a commensal?
An orgnanism thats part of a normal flora (E Coli in the gut) ( Staph Aureus in the nose)
Define Pathogenicity:
The capactiy of a micro-organism to cause an infection.
(Infectivity &Virulence)
What makes up a pathogen’s Infectivity?
- Attachment e.g. E. Coli use fimbraie & receptors on uroepthelial cells
- Acid Resistance e.g. Helicobacter pylori uses urease to make ammonia from urea
What makes up a viruses virulence?
Invasiveness
Toxin prodcution
Evasion of immune system
Describe examples of how bacteria (e.g. Step. Pyogenes) invade tissues:
Bacterial invasiness can include:
- Necrotising fasciitis (flesh-eating)
- Cellulitis
- Connective Tissue Breakdown
- Fibrinolysis
Define exotoxin:
Toxins released extracellularly by the micro-organism
Define Enterotoxin:
Exotoxins which act on the GI tract
Define Endotoxin:
A toxin structurally part of the gram -ve cell wall
E,g, lipid A in lipopolysaccharide layer
How does clostridium tetani work?
The exotoxin of Tetanus.
Binds to nerve synapses ihibiting release of inhibitory neurotransmitters (paralysis)
How does cholera enterotoxin work?
Increases cAMP level
- Inhibits uptake of NA+ & Cl- ions
- Strimulates secretion of Cl- & HCO3- ions
death by dehydration
What is the main endotoxin & how it works?
Lipid A in the lipopolysaccharide layer.
Induces sever uncontrolled host response e.g. fever, rigors, tachycardia, cytokine production etc
Define pathogenic bacteria?
Thsoe capable of causing disease
Requirment sof pathogenicity are?
Infectivity & virulence
What makes up virulence?
Invasiveness
Toxin production
Immune evasion
