Session 5 Flashcards
Define a surface.
An interface between a solid and either a liquid or gas.
What bacteria are normally present on skin?
Staphylococcus aureus, coagulase negative Staphylococci, corynebacterium, enterobacteriaceae.
How can different staphylococci be distinguished?
Via coagulase testing: Staphylococcus aureus is coagulase positive, the rest are coagulase negative.
How is coagulase testing performed?
Bacteria are introduced to rabbit plasma and incubated; if a mass of coagulated plasma forms then coagulase is present (therefore is Staphylococcus aureus).
Why is coagulase useful to bacteria?
Acts as a virulence factor and can ward off neutrophils so the bacteria is more resistant to clearance.
What are microbiota?
Bacteria normally found in an area of the body: commensals.
How may microbiota be useful?
May produce vitamins, aid in digestion, and prevent harmful bacteria from colonising.
How may microbiota lead to infection?
If transferred to other sites by direct contiguous spread, migration, inoculation or haematogenous spread.
What can prosthetic valve endocarditis be caused by?
Coagulase negative streptococci, Enterococcus faecalis, Staphylococcus aureus or Candida albicans.
What is prosthetic valve endocarditis likely to be caused by if it develops soon after the operation?
Coagulase negative streptococci.
What are prosthetic joint infections usually caused by?
Coagulase negative staphylococci or staphylococcus aureus.
What is cardiac pacing wire endocarditis usually caused by?
Coagulase negative staphylococci or Staphylococcus aureus.
How do biofilms form?
Bacteria attach to a surface; they multiply and form a slimy matrix to encase the colony; nutrients diffuse through the colony and micro-environments are formed; colony communicates via quorum signalling; some bacteria may break off from the colony and move but remain protected by the biofilm.
