Pathogens and Hosts Flashcards
What are the characterised signs and symptoms of clinical infection?
Inflammation Pain Raised body temp - pyrexia Rigors - body shaking violently Increased WBC Increased C reactive protein
What is a pathogen?
An organism which causes disease
What is a commensal?
An organism which is part of normal flora - doesn’t necessarily cause illness
Give an example of commensal
E.coli in the gut
What are the rules of Koch’s Postulates?
Organisms must be found in all cases of the disease
Must be able to be cultured outwith the body
Should reproduce the disease on inoculation
What is the pathogenicity of a micro- organism?
Its capacity to cause an infection
What are the requirements of pathogenicity?
Infectivity
Virulence
What is infectivity of a pathogen?
the ability to become established on or within a host
What is the virulence of a pathogen?
Its ability to cause harmful effect to the host once established
Do different strains of the same micro- organisms behave all the same?
No - different strains can behave very differently
What is the virulence specific to?
Strains not species
The harm that a pathogen causes is conferred by what/
Virulence factors
Where are exotoxins released?
Extracellularly by the micro-organism
Where do enterotoxins act on?
The GI tract
What are endotoxins structurally part of?
The gram negative cell wall
Give an example of an exotoxin
Tetanus - infection of dirty wounds
Give an example of an enterotoxin
Cholera - colonises small intestine
Are superantigens certain exotoxins or enterotoxins?
Certain exotoxins
What are superantigens able to do?
Stimulate division of T cells in the absence of that specific antigen
What do superantigens cause an overwhelming production of and what does this cause?
Cytokines
Causing toxic shock
What specifically is an endotoxin a component of?
Gram negative bacterial cell wall
Lipopolysaccharide
Lipid A
What is virulence conferred by?
Invasiveness, toxin production and immune evasion
What are harmful effects in immunity caused by?
The effects of the bacterium
The hosts response
Or both
