Mechanisms of antibiotic resistance

Question 1

How do antibiotic resistance strains affect treatment?

Answer 1

• Risk of over treatment if resistance taken into account i.e. broad spectrum -> resistance
• Risk of under treatment i.e. if traditional antibiotics used
• Use of alternative treatments which are expensive, last line or toxic

Question 2

Sensitivity testing - what does a greater zone of inhibition mean?

Answer 2

greater sensitivity to antibiotic (susceptible)

Question 3

Mechanisms of drug resistance (5)

Answer 3

• no target = no effect
• Reduced permeability (drug can’t get in!)
• Enzymatic degredation
• Altered target (mutations)
• Drug efflux

Question 4

Absent target example

Answer 4

Treating infection that is non-bacterial

Question 5

Reduced permeability examples

Answer 5

• Vancomycin has no effect on gram- bacteria

- Gentamicin - no effect on anaerobic organisms (uptake = O2 dependent)

Question 6

Target alteration example

Answer 6

MRSA - altered penecillin binding protein does not bind Blactams

Question 7

Enzymatic degredation example

Answer 7

penecillin and cephalosporins; B lactamases - breaks them down

Question 8

Where are resistance genes encoded?

Answer 8

PLASMIDS

Question 9

Name the mechanism by which resistance is transferred

Answer 9

Conjugation

Question 10

What is meant by horizontal transfer of resistance?

Answer 10

Transferred between organisms - transporins and interns

Question 11

What is meant by vertical transfer of resistance?

Answer 11

Resistance transferred to daughter cells of bacterial cell division