Pathogens of the host Flashcards
What is a commensal
Organism part of normal flora
Pathogenicity
The capacity of a micro-organism to cause an infection
Pathogenicity requires
Infectivity -Ability to become established
Virulence - Ability to cause harmful effects once established
The ability to become established within a host dependant on
Pathogens attachment
pathogens acid resistance (e.g. high acidic level in the stomach)
Pathogen
organism that causes a disease
What is virulence
ability to cause harmful effects once established
What are the three virulence factors
Invasivness
Toxin production
evasion of immune system
What is virulence specific to
strains not species
What is invasiveness
Multiplies and spreads around the body
what is toxin production
release toxins extracellular
Streptococcus pyogenes is an invasive bacteria causes what disorders
Necrotising fasciitis
Cellulitis
Connective tissue breakdown
Fibrinolysis - the enzymatic breakdown of the fibrin in blood clots
What is released extracellularly by the micrograms
exotoxins
what are enterotoxins
more specific exotoxins which act on the GI tract
what is endotoxin
structurally part of the Gram negative cell wall that is release when disintegrates
What bacteria causes tetnus and what does it produce
clostridium tetani
an exotoxin
When and what does tetanus do
How is death caused?
Happens through contaminated wounds
toxin production binds to nerve synapse and inhibits release of inhibitory neurotransmitters.
death = respiratory paralysis
How is tetanus treated
debridement (removal of damaged tissue), antibiotics and antitoxin
What bacteria is cholera and what does it produce
Vibrio cholerae, enterotoxin
What does cholera enterotoxin do
Increases cAMP levels which inhibits uptake of Na and Cl ions causes outflow of water into GI tract resulting in dehydration due to watery diarrhoea
What are the two example of bacteria which produce superantigens
Strep pyogenes and Staph aureus
What are two examples of the commensal flora in the gut and nose
E. Coli - Gut
Staph. aureus - Nose
What do super antigens do
able to stimulate t cells proliferation therefore increasing cytosine resulting in toxic shock
What part of the gram negative bacterial cell wall is the endotoxin
Lipid A
What are the seven things that characterise infection
Inflammation Pain Pyrexia (fever) Tachycardia Rigors (sustained shaking) Increased white cell count Increased C reactive protein (markers of infection)
What does it mean if someone is asymptomatic
Shows no symptoms
