Antibiotics a logical approach

Question 1

Gram +ve

Answer 1

Thick peptidoglycan cell wall

Question 2

Gram -ve

Answer 2

Thin peptidoglycan cell wall

Question 3

B lactam examples

Answer 3

Penicillin, cephalosporins, vancomycin

Question 4

B-lactam antibiotic method of action

Answer 4

Inhibit cell wall synthesis

Question 5

Macrolides and clindamycin

Answer 5

Inhibit 50S subunit + protein synthesis

Question 6

Aminoglycosides and tetracyclines

Answer 6

Inhibit 30S subunit + protein synthesis

Question 7

MOA of quinolones

Answer 7

Inhibit DNA gyrase and stop nucleic acid synthesis

Question 8

MOA of trimethoprim

Answer 8

Inhibit folate synthesis to stop nucleic acid synthesis

Question 9

MOA of nitrofurantoin

Answer 9

Create free radicals and inhibit nucleic acid synthesis

Question 10

Penecillin MoA

Answer 10

Inhibit cell wall synthesis by preventing peptidoglycan cross-linkage which weakens wall
Irreversible binding to transpeptidase enzymes in cell wall

Question 11

B-lactamase MoA

Answer 11

Hydrolyses the B-lactam ring to stop penicillin activity

Question 12

Clavulanic acid MoA

Answer 12

Re-activates penicillin by inactivating B-lactamase

Question 13

S/e of penicillin

Answer 13

Rash, nausea, vomiting, diarrhoea

Question 14

Cephalosporin structure

Answer 14

B-lactam ring fuses with dihydrothiazine ring to produce cephem nucleus

Question 15

How do cephalosporins work?

Answer 15

Disrupts the integrity of the peptidoglycan cell wall

Question 16

Why are cephalosporins less susceptible to B-lactamase

Answer 16

Modified B-lactam ring is more stable

Question 17

Where are cephalosporins excreted?

Answer 17

Liver

Question 18

MoA vancomycin

Answer 18

Inhibits cell wall synthesis but non B-lactam bactericidal

Question 19

When will vancomycin be used?

Answer 19

Aerobic and anaerobic gram -ve bacteria inc MRSA

C.diff and endocarditis

Question 20

MoA macrolides

Answer 20

Inhibits bacterial protein synthesis

Stops translocation movement of ribosomes so it can’t create protein chain

Question 21

Macrolides example

Answer 21

Erythromycin

Question 22

S/e macrolides

Answer 22

Nausea, vomiting, diarrhoea

Question 23

Why are macrocodes dangerous

Answer 23

Interacts with warfarin, simvastatin and carbamazepine

Question 24

MoA gentamicin

Answer 24

Inhibits protein synthesis by binding to S30 tRNA

Question 25

Why does gentamicin need to be administered via IV

Answer 25

Large polar molecule

Low protein binding - water soluble

Question 26

How is gentamicin excreted

Answer 26

urine

Question 27

side effects gentamicin

Answer 27

Ototoxicity and nephrotoxicity

Question 28

MoA ciprofloxacin

Answer 28

Blocks DNA replication - circular DNA rings need topoisomerase to unwind two strands to replicate. Fluroquinolones inhibit this process - bacteriostatic

Question 29

MoA trimethoprim sulfamethoxazole

Answer 29

Inhibits folic acid synthesis in bacteria but huge amount needed to affect human cells

Question 30

STevens-Johnson side effect

Answer 30

Skin reaction

Question 31

Metronidazole

Answer 31

Effective against anaerobes, little resistance

Enters bacteria by passive diffusion

Question 32

Metronidazole MOA

Answer 32

Induces DNA breakage

Question 33

Where is metronidazole metabolised and excreted?

Answer 33

liver and kidney

Question 34

What is MRSA

Answer 34

Methicillin resistant staphylococcus aureus