Antibiotic classes

Question 1

Mode of action of aminoglycosides

Answer 1

Bind irreversibly to 30s subunit of bacterial ribosomes and inhibit protein synthesis

Question 2

Aminoglycosides can be used against

Answer 2

gram negative aerobic bacteria, staphylococci, mycobacteria

Question 3

mechanism of resistance

Answer 3

strep and anaerobic bacteria get rid of their oxygen-dependant transport system through which aminoglycosides usually enter
other bac: reduce cell membrane permeability, acquire enzymes that modify aminoglycosides

Question 4

inhibit enzymes responsible for cross-linking peptidoglycans in bacterial cell walls during cell growth -> cell walls unable to maintain osmotic gradient -> cell swelling, lysis, death

Answer 4

carbapenems/cephalosporins

Question 5

macrolides used against

Answer 5

broad spectrum, synthetic macrolides eg clari/azithro increasingly work better against gram negative

Question 6

bind to 50s subunit of ribosome, inhibit protein synthesis, blocks process of elongation of polypeptide chain. bacteriostatic.

Answer 6

macrolides

Question 7

metronidazole -> efficacious against?

Answer 7

anaerobic bac only. resistance to it is low

Question 8

metronidazole mode of action

Answer 8

reduction of metronidazole produces free radical -> reduces DNA synthesis -> degradation + cell death

Question 9

for urinary infections by either gram + or -

Answer 9

nitrofurantoin

Question 10

nitrofurantoin mode of action

Answer 10

reduced by nitrofurantoin reductase to active metabolite which damages bac DNA –> cell death

Question 11

reduction of nitrofuran reductase activity causes

Answer 11

nitrofurantoin resistance

Question 12

inhibit enzymes responsible for peptidoglycan cross-linking -> weak cell wall -> swelling -> lysis -> death

Answer 12

penicillins

Question 13

beta-lactamase

Answer 13

breaks beta lactam ring -> prevents beta-lactamase activity

Question 14

how is penicillin specificity established?

Answer 14

side-chains attached to beta-lactam ring can be modified

Question 15

quinolone mode of action

Answer 15

block topoisomerase enzymes -> inhibit DNA synthesis

Question 16

bacterial quickly develop resistance to…

Answer 16

quinolones. some prevent intracellular accumulation by reducing permeability and/or increasing efflux / mutations in target enzymes

Question 17

tetracyclines

Answer 17

broad spectrum

Question 18

bind to 30s ribosomal subunit, prevents binding of tRNA to mRNA -> prevents new addition of amino acids to growing polypeptide chains -> bacteriostatic

Answer 18

tetracycline

Question 19

efflux pump

Answer 19

common method of tetracycline resistance

Question 20

trimethoprim

Answer 20

broad spectrum of action against gram + and - bacteria particularly enterobacteria eg E coli

Question 21

inhibits bacterial folate synthesis, slowing bacterial growth -> bacteriostatic

Answer 21

trimethoprim

Question 22

vancomycin

Answer 22

gram + aerobic and anaerobic bacteria

Question 23

inhibits growth and cross-linking of peptidoglycan chains -> inhibits cell wall synthesis (gram + only)

Answer 23

vancomycin