Lecture 10- Staphylococcus Aureus

Question 1

colinisation is common or uncommon

Answer 1

common

Question 2

when is the peak incidence?

Answer 2

first year of life and then decline as you age.

Question 3

how does staph. aureus evade the immune system?

Answer 3

coats itself in antibody, clotting proteins, sugar capsule to avoid being detected by white blood cells.
release chemicals (CHIPS) to prevent chemotaxis
use an enzyme (catalase) to breakdown hydrogen peroxide inside neutrophils
release a toxin (haemolysin, PVL) to destroy neutrophils

Question 4

Treatment of Stap. aureus infection

Answer 4

1. stabalise patient
2. drain puss- surgery/intervention
3. antibiotics that disrupt the cell wall and interfere with protein synthesis

Question 5

Penicillins function in bacteria

Answer 5

inhibits transpeptidase a bacterial enzyme that cross links the sugars of peptidoglycan and provides structural integrity of the bacterial cell wall- makes them explode. staph. aureus created an enzyme to dissolve this antibiotic

Question 6

methicillin and staph. aureus

Answer 6

staph. aureus changed the target for methicilin and became resistant (MRSA). in 2013 77% were resistant to penicillin and 12% resistant to methicillin.

Question 7

most common colonisation sites for staph.

Answer 7

nose is most common

Question 8

nasal carriers

Answer 8

persistant intermittent (15%)- carry increased risk of disease
non (25%)-carry decreased risk of disease.

Question 9

nasal colonisation

Answer 9

SA invokes an asymptomatic immune response in the nose
nasal secretions change in the presence of SA
“persistant carrier” have immune differences to “persistant” non carrier
about 20-25% colonisation