Week 2 - antimicrobials

Question 1

how can antibacterial agents be classified?

Answer 1

1. bactericidal or bacteriostatic
2. target site (mechanism of action)
3. chemical structure (antibacterial class)
4. spectrum (broad or narrow - action)

Question 2

what are the different types of antimicrobials possible?

Answer 2

antibacterial
anti-fungal
antiviral
antiprotozoal agents

Question 3

what are the ideal features of antimicrobial agents?

Answer 3

1. selectively toxic
2. few adverse effects
3. reach site of infection (bloodstream / CSF)
4. oral / IV formulation
5. long 1/2 life (infrequent dosing)
6. no interference with other drugs

Question 4

what are the classes of antibacterials and their mechanisms of action? (what can the antibacterial affect?)

Answer 4

cell wall synthesis
protein synthesis
nucleic acid synthesis
cell membrane function

Question 5

example of a drugs affecting cell wall synthesis?

Answer 5

beta-lactams

glycopeptides

Question 6

example of drugs affecting protein synthesis?

Answer 6

tetracyclines
aminoglycosides
macrolides

Question 7

example of drug affecting nucleic acid synthesis?

Answer 7

quinolones

Question 8

examples of drug affecting cell membrane function?

Answer 8

(not as commonly used)

polymixins

Question 9

how does penicillin work?

Answer 9

interfere with the protein which reinforces rigidity of cell wall (cross linkage) - inhibiting the growth of the cell
(penicillin binds to the protein which allows cross linkage)

Question 10

how does vancomycin work?

Answer 10

sits on cross linking chains and prevents penicillin binding protein to join onto cross link to join them together - binds to the separate chains

Question 11

How do Fluoroquinolones work?

Answer 11

bind to 2 nuclear enzymes, inhibiting DNA replication

affecting nucleic acid synthesis

Question 12

what are the different mechanisms of resistance?

Answer 12

1. drug inactivating enzymes
2. altered target
3. altered uptake

Question 13

how do drug inactivating enzymes work?

Answer 13

microorganisms produces inactivating enzymes that destroys the antibiotic drug before it can act on the microorganism - enzyme destroys drug

Question 14

what is an example of a drug inactivating enzyme?

Answer 14

B-lactamases

aminoglycoside enzymes

Question 15

how do altered target resistance work?

Answer 15

target enzyme has lowered affinity for antibacterial
(the target for the activity of the organism is changed, so the antibiotic is no longer as effective because the target has changed)

Question 16

what is an example of altered target resistance?

Answer 16

meticillin (MRSA)

Question 17

how does altered uptake resistance work?

Answer 17

1. decrease permeability

2. increase efflux

Question 18

explain decreased permeability in altered uptake resistance

Answer 18

inability of antibiotic to penetrate into the cell - drug can’t get into cell

Question 19

explain increase efflux of altered uptake

Answer 19

microorganism has an active pump which pumps the antibiotic out of the cell before it can take effect - efflux
drug sent out of cell via active pumping

Question 20

example of decrease permeability and increase efflux?

Answer 20

1. B-lactams

2. tetracyclines

Question 21

what are the genetic basis of antibiotic resistance?

Answer 21

1. chromosomal gene mutation

2. horizontal gene transfer

Question 22

explain chromosomal gene mutation

Answer 22

mutated gene containing resistance in a cell survives antibiotic
antibiotic resistance selected and multiply and can be spread onto other patients to spread resistance

Question 23

what are the different components that can take part in horizontal gene transfer?

Answer 23

1. chromosome
2. plasmid
3. transposon

Question 24

what are the different methods of horizontal gene transfer?

Answer 24

1. conjugation
2. transduction
3. transformation

Question 25

what is conjugation?

Answer 25

sexual process between 2 microorganisms - transfer

Question 26

what is transduction and what does it use?

Answer 26

viruses that can affect microorganisms - phages

Question 27

what is transformation?

Answer 27

free genetic material (e.g. DNA) that can pass directly through the cell wall into the organism

Question 28

what are the different types of horizontal gene transfer that are passed onto the next generation of microorganisms?

Answer 28

1. cell replication - plasmid
2. plasmid integrated within the bacterial DNA, so when cell replicates, the integrated plasmid is replicated as well (plasmid integrated into nucleus)

Question 29

what is the minimum inhibitory concentration (MIC)?

Answer 29

the minimum concentration of antibiotic required to inhibit bacterial growth