2.2 Antimicrobial agents

Question 1

antibiotic mechanisms (4)

Answer 1

1 inhibit cell wall synthesis
2 inhibit protein synthesis
3 interferes with DNA synthesis and replication
4 disrupts cell membrane

Question 2

what antibiotics inhibit cell wall synthesis

Answer 2

beta lactam and glycopeptide

Question 3

beta lactam antibiotic examples

Answer 3

penicillins, cephalosporins and carbapenems
beta lactams contain a ring of carbons and modifiable residues
have been many generations of cephalosporins
carbapenems are last line antibiotics, main one is meropenem which is broad spectrum

Question 4

describe beta lactam mode of action

Answer 4

penicillin blocks the active site through penicillin binding protein so the bacteria can’t form the cell wall properly and it breaks open (think of it as punching holes in cell wall)
Inhibiting transpeptidases from linking amino acid side chains.

Question 5

what are beta lactamase inhibitors and why are they needed

Answer 5

bacteria produce beta lactamases to hydrolyse the beta lactam ring of antibiotic to make it ineffective. So beta lactamase inhibitors block their active site to prevent them destroying the antibiotic, such as clavulanic acid, to leave the antibiotic free to work. E.g. co-amoxiclav= amoxicillin and clavulanic acid

Question 6

glycopeptide antibiotics examples

Answer 6

vancomycin and teicoplanin, have broad gram positive spectrum

Question 7

describe glycopeptide mode of action and how resistance occurs

Answer 7

they bind directly to amino acid side chains, so cell wall cross-linking enzymes can’t attach, resistance occurs when bacteria modify side chain structures

Question 8

give examples of antibiotics that inhibit protein synthesis, will they have an immediate effect?

Answer 8

macrolides, tetracyclines and aminoglycosides
they may not have an immediate effect with bacteria need to constantly turn protein over so blocking this will interfere with growth

Question 9

example of macrolides

Answer 9

clarithromycin- used to treat community acquired pneumonia

Question 10

example of tetracyclines

Answer 10

Doxycycline- oral and long lasting, used in COPD

Question 11

example of aminoglycosides

Answer 11

gentamicin- narrow therapeutic window since can damage kidneys, used for sepsis

Question 12

give examples of antibiotics that inhibit DNA synthesis and replication

Answer 12

sulphonamides, diaminopyrimidines and quinolones

Question 13

what do antibiotics that inhibit DNA synthesis and replication exploit

Answer 13

the fact that bacteria have to synthesis folate and cannot absorb it, they interfere with folate synthesis at different stages, use more than one to be more powerful and reduce the chance of resistance (synergistic activity)

Question 14

what is fluroquinolone and what is it used for

Answer 14

fluorine atom and quinolone, stops DNA unwinding before replication by binding to 2 nuclear enzymes. Causes shredded DNA, rapidly fatal to bacteria

Question 15

fungi are (p or e)

Answer 15

eukaryotes (have a nucleus)

Question 16

what is mycosis

Answer 16

a disease caused by fungal infection

Question 17

give 3 examples of antifungal drug types

Answer 17

azoles, polyenes and echinocandins

Question 18

surgical patients are prone to infections of

Answer 18

candida- lots in the gut

Question 19

explain antifungal mode of actions

Answer 19

cell wall is ergosterol based rather than human cholesterol, so they interfere with the ergosterol pathway or bind directly to it

Question 20

what antibiotics act on the 30s ribosomal subunit

Answer 20

aminoglycosides and tetracyclines

Question 21

what antibiotics act on the 50s ribosomal subunit

Answer 21

macrolides and chloramphenicol

Question 22

give an example of triazoles, polyenes and echinocandins

Answer 22

fluconazole (broad), amphotericin B (I.V for systemic mycoses) and caspofungin (less toxic than Amph.B)

Question 23

give an example of penicilins, cephalosporins and carbapenems

Answer 23

flucloxacillin, cefalexin and ertapenem