Staphylococcus Flashcards
What does staphylococcus mean?
Staphyle = Bunch of grapes, Kokkos = grain or berry
Facutatively
Adaptable to a certain way - e.g. facultative anaerobe canbe anearobe
Staphylococcus general traits:
1) Facutatively anaerobic
2) gram positive
3) Catalase positive (hydrogen peroxide can be broken down)
4) resistant to dry and high salt
Where are staphylococci normally found?
The skin, but are very resistant in general environment (also upper resp. and microbiota)
What is a pyogenic infection?
One that produces pus - often cyst and lumps
What is the major pathogenic staphylococci?
Staphylococci aureus.
How is staphylococci aureus characterized?
By its ability to coagulate blood (coagulase positive)
Where does tyhe name aereus come from?
The fact that the colonies they form on agar is a bit yellow.
Main diagnostic features of staphylococcus aureus:
1) Coagulase (fibrinogen to fibrin)
2) Production of nuclease that breaks down DNA
3) Surface protein known as clumping factor that further associates to coagulation
Where is staph. aureus found?
30 % of healthy people have it in the nose - on skin as well.
When does staph. aureus cause infection?
Lowered host defences (skin lesions etc)
Staph aureus toxins
1) Enterotoxins (protein exotoxin that particularly affects gastro-intenstinal tract -often by altering membrane permability)-food poisoning
2) Toxic shock syndrome toxin (TSST)
3) Epidermolytic toxins (destroys epidermal membrane - two types A and B)
4) PVL (Panton-Valentine leukocidine)
Staph. Aureus source of infection:
1) contact with infected lesions
2) Healthy carriers
3) Animals (like from milk - food poisoningfrom enterotoxins)
4) From the environment (not spores though)
MRSA
Methicilin (beta lactam ring that inhibits peptidoglycan synthesis) resistant staphylococcus aureus - makes penicilin binding protein
endemic in most hospsitals around the world.
Collection places of staph. aureus for diagnosis:
1) Pus from wound
2) sputum (mucus from lower airways) from people with pneumonia
3) Faeces from patientrs with food poisoning)
4) Urine from patients (cystitis)
5) nasal swab for carriers
