Microbiology Flashcards
what are virulence factors
molecules produced by pathogens that contribute to the pathogenicity of the organism
what is the pathogenesis of bacteria
1- Contact/entry host 2 - Adhere/Colonise and invade 3 - Evade host defences 4 - Multiply/complete its life cycle 5 - exit host 6 - release/spread 7 - reservoir of pathogens
what is virulence
the capacity of a micro-organism to cause disease/damage to the hose
what are the virulence factors
adhesin invasin impedin aggressin modulin
what is adhesin
enabled binding of the organism to host tissue
what is invasin
enables the organism to invade a host cell/tissue
what is impedin
enables the organism to avoid host defence mechanism
what is aggressin
causes damage to the host directly
what is modulin
induces damage to the host indirectly
what VF are responsible for variation
adhesin, impedin, aggressin
what are the VF of S.aureus
firbinogen binding protein
leukocidin (PVL)
TSST-1 (toxin)
what are examples of adhesins/attachment
fibrinogen-binding
collagen-binding
what helps with evasion of host defences
supertoxins
PVL
alpha toxin
what is PVL
Panton-Valentine Leukocidin
produced by some strains of Staph Aureus
has toxicity for leukocytes
associated with severe skin infections
what is PVL and alpha toxin linked with
CA-MRSA responsible for necrotising pneumonia and contagious severe skin infections
what are superantigens
class of antigens that cause non-specific activation of T-cells resulting in polyclonal T cell activation and massive cytokine release
what super antigen is associated with toxic shock
TSST-1
what is the diagnostic criteria for toxic shock
fever
diffuse macular rash
hypotension
more or equal to 3 organ systems involved (liver, blood, renal, mucous membranes, GI, MSK, CNS)
what skin infections does strep. pyogenes cause
impetigo
cellulitis
necrotising fasciitis
toxic shock like syndrome (TSLS)
what is special about strep. pyogenes
beta haemolysis
GAS