Lecture 15 - Antimicrobial mechanisms and Resistance

Question 1

Difference between antibiotics and chemotherapeutic agents

Answer 1

Antibiotics are naturally-occurring

Chemotherapeutic agents are synthetic

Question 2

Goal of semi-synthetic drugs
1)
2)
3)

Answer 2

1) Alter kinetics
2) Reduce toxicity
3) Broaden antimicrobial spectrum

Question 3

When might it be useful for a drug to have a short half life?

Answer 3

If excreted by the kidneys, for a UTI

Increases the amount of antimicrobial in the urinary tract

Question 4

Which type of bacterium is Bordatella?

Answer 4

Gram - rod

Question 5

Bordatella intrinsic resistance

Answer 5

Intrinsically resistant to penicillin

Question 6

Phases of bacterial growth curve
1)
2)
3)

Answer 6

1) Lag phase
2) Exponential phase
3) Stationary phase

Question 7

What qualifies an antimicrobial as bactericidal?

Answer 7

Kills 99.9% of bacteria

3-log reduction (log10 scale)

Question 8

When are bactericidal antimicrobials necessary?

Answer 8

In immunocompromised patients

Question 9

Tetracycline structure

Answer 9

Four hexagonal carbon rings

Question 10

Structural difference between penicillin and cephalosporin beta-lactams

Answer 10

Penicillin is a beta-lactam ring attached to a pentagonal structure

Cephalosporins are beta lactam ring attached to a hexagonal structure

Question 11

Tetracycline pharmacokinetics

Answer 11

Very short half-life

Excreted in bile

Question 12

How are tetracyclines excreted?

Answer 12

In bile

Question 13

Penicillin examples
1)
2)
3)
4)
5)
6)

Answer 13

1) Penicillin G
2) Penicillin V
3) Ampicillin
4) Methicillin
5) Flucloxacillin
6) Carbenecillin

Question 14

Penicillin G oral availability

Answer 14

Low

Question 15

Penicillin V oral availability

Answer 15

Good

Question 16

Organisms susceptible to penicillin G

Answer 16

Gram + rods, cocci

Gram - cocci

Question 17

Organisms susceptible to penicillin V

Answer 17

Gram +rods, cocci

Gram - cocci

Question 18

Toxicity of penicillin G and V

Answer 18

Very low

Question 19

Organisms susceptible to ampicillin

Answer 19

Gram + rods, cocci

Gram - rods, cocci

Question 20

Ampicillin oral availability

Answer 20

Good

Question 21

Ampicillin toxicity

Answer 21

Very low

Question 22

Methicillin toxicity

Answer 22

Moderate

Question 23

Organisms susceptible to methicillin

Answer 23

Gram + cocci

Targeted against staphylococci

Question 24

Methicillin oral efficacy

Answer 24

Poor

Question 25

Organisms susceptible to flucloxacillin

Answer 25

Gram + cocci

Targeted against staphylococci

Question 26

Flucloxacillin toxicity

Answer 26

Low

Question 27

Flucloxacillin oral availability

Answer 27

Good

Question 28

Carbenecillin oral availability

Answer 28

Poor

Question 29

Organisms susceptible to carbenecillin

Answer 29

Gram - rods

Targeted against pseudomonas

Question 30

Antimicrobials used particularly against gram + cocci, EG: staphylococcus

Answer 30

Methicillin, flucloxacillin

Question 31

Antimicrobial particularly used against G- rods, EG: pseudomonas

Answer 31

Carbenicillin

Question 32

Carbenecillin toxicity

Answer 32

Very low

Question 33

Antimicrobials targeting cell wall
1)
2)

Answer 33

1) Beta lactams

2) Glycopeptides

Question 34

Antimicrobials targeting cytoplasmic membrane
1)
2)

Answer 34

1) Polymixins (antibacterial)

2) Polyenes (antifungal)

Question 35

Antimicrobials targeting ribosomes
1)
2)

Answer 35

1) Aminoglycosides

2) Chloramphenicol

Question 36

Antimicrobials targeting nucleic acids
1)
2)

Answer 36

1) Rifamycins

2) Quinolone

Question 37

Antimicrobials targeting folic acid synthesis
1)
2)

Answer 37

1) Sulphonamides

2) Trimethoprim

Question 38

Bacteria innately resistant to sulphanomides

Answer 38

Enterococci

Can’t synthesise folate

Question 39

Can humans synthesise folate?

Answer 39

No

Question 40

Examples of bacteria to be treated with ampicillin

Answer 40

Salmonella

Haemophilus influenzae

Question 41

Which antimicrobial would salmonella and H. influenzae be treated with?

Answer 41

Ampicillin