Antibiotics

Question 1

List 3 antibiotics uses/therapies

Answer 1

Guided therapy
Empirical therapy
Prophylactic therapy

Question 2

Describe guided therapy

Answer 2

For mild infections that are not severe/urgent

antibiotic given which is known to be effective

Question 3

Describe empirical therapy

Answer 3

for severe infections where waiting could be dangerous
Best educated guess according to what you know about patient on what is likely to be effective, not enough time to wait for a culture.

Question 4

Compare guided and empirical therapy according to:
action on bacteria
penetration to site
impact on colonisation and resistance 
spectrum type

Answer 4

Guided:
Limited action on bacteria causing infection
Try to limit penetration to site of infection
Little impact on colonisation and bacteria
NARROW spectrum - active against a selective group of bacteria

Empirical:
Broad, extensive action against bacteria
Need to penetrate broadly throughout body
Accept that impact on colonisation and resistance may be greater
BROAD spectrum - active against a wide range of bacteria

Question 5

Describe bacteriostatic agents and give an example

Answer 5

Inhibits bacteria but does not directly kill it.
Requires additional factors to kill it.
e.g. clarithromycin

Question 6

Describe bactericidal agents and give an example

Answer 6

Directly kills bacteria
Rapid lysis of bacteria can sometimes lead to release of toxins and anti-inflammatory agents
e.g. penicillin

Question 7

compare what happens once bactericidal and bacteriostatic bacteria are removed?

Answer 7

When bacteriostatic is removed: bacteria is left behind. usually the immune system completes the job.

When bactericidal is removed: bacteria has been cleared

Question 8

Which bacteria type is better at resisting antibiotics?

Answer 8

Gram negative bacteria

Question 9

list the common targets for antibiotics and examples of antibiotics which target them

Answer 9

Cell wall agents: penicillin and glycopeptides
Ribosome: Macrolides and Aminoglycosides
DNA: quinolones
Metabolism: trimethoprim

Question 10

Describe the mechanism of penicillin

Answer 10

Inhibits polymerisation and cross-linking of peptidoglycan

Question 11

Describe the mechanism of glycopeptides and what type of bacteria are they most effective against?

Answer 11

Directly inhibit cell wall synthesis

Effective against gram positive bacteria

Question 12

what type of agents are antibiotics that target ribosomes?

Answer 12

Bacteriostatic agents

Question 13

Describe the mechanism of macrolides

Answer 13

Bind to and inhibits bacterial ribosomes

Question 14

Describe the mechanism of aminoglycosides

Answer 14

Binds to the 30S ribosome and inhibits protein synthesis

Question 15

Describe the mechanism of quinolone

Answer 15

Inhibits DNA gyrase and inhibits DNA replication

Question 16

Describe the mechanism of trimethoprim

Answer 16

Inhibits folate metabolism and terminates DNA synthesis

Question 17

Describe the 3 mechanisms of antibiotic resistance

Answer 17

Mutation of target site (no longer binds)
Inactivating enzymes (enzymes that inactivate antibiotics)
Limting access by changing exterior surface: increasing efflux (material flowing out), reducing permeability