microbiology Flashcards
what is an adhesin
enables binding of the organism to host tissue
what is invasion
enables the organism to invade a host cell/tissue
what is impedin
enables the organism to avoid host defence mechanisms
what is aggressin
causes damage to the host directly
what is modulin
induces damage to the host indirectly
what are toxinoses
single component, can be made of multiple proteins, acting on distinct targets exported from infectious agent
TSST-1, staphylococcal food poisoning, SSS
what are superantigens
common theme disrupting immune system and co-ordination by over stimulation
what is the diagnostic criteria for toxic shock syndrome
fever
diffuse macular rash and desquamation
hypotension
>= organ systems involved
examples of adhesins
- extra cellular matrix molecules
- fibrinogen binding
- fibronectin binding
- collagen binding
- elastin binding protein
what is lancefield system
Lancefield grouping is a system of classification that classifies catalase-negative Gram-positive cocci based on the carbohydrate composition of bacterial antigens found on their cell walls
examples of GAS skin diseases
impetigo
cellulitis
erysipelas
where does staphylococcus colonise?
sebaceous gland
what are some staph aureus skin presentations
rash folliculitis abscess carbuncle impetigo scalded skin syndrome
is S.aureus coagulase positive or negative
positive
is s.epidermis coagulase positive or negative
negative
what % colonisation is S. aureus
20
what % colonisation is S. epidermis
100
symptoms of TSST-1
rapid progression, high fever, vomiting, diarrhoea, sore throat, muscle pain
diffuse macular rash and desquamation, hypotension
superantigen
toxic shock
activate 1 in 5 T cells
massive release of cytokines and inappropriate immune response
what is panton-valentine leukocidin
specific secreted proteins that form one functional complex that attacks white blood cells
very damaging and can mean death
what is necrotizing pneumonia
severe complication of quite mild infections due to destruction of immune cells
what type of haemolysis is alpha haemolysis and what colour is it
partial on blood agar and green
what type of haemolysis is beta and what colour
complete on blood agar and clear
what type of haemolysis is gamma and what colour
no haemolysis on blood agar
example of an iGAS disease
necrotizing fasciitis
- invasive strep A strains penetrate mucous membrane and develop in lesion
- severe infection
what is streptolysin S (SLS)
- pore forming cytolysin
- toxic to PMN, organelles, platelets
- important in animal models
- responsible for beta haemolysis
