beta lactam antibiotics and vancomycin Flashcards

1
Q

Why is the bacterial cell wall a drug target?

A

because humans don’t have cell walls. The formation of cell walls are prevented rather than the destruction of made cell walls because they are very tough so its easier to prevent their synthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the main structural differences between gram positive and gram negative cell walls?

A

+ve: thick peptidoglycan layer, techoic acids

-ve: thin peptidoglycan layer, outer membrane layer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the function of the cell wall?

A
  • to maintain cell shape
  • to protect the membrane from rupturing as osmotic pressure is high inside the cell meaning high salt conc, therefore high water conc
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Give an example of norcardiform bacteria and why are they difficult to stain?

A

mycobacteria = TB
They are gram +ve but are difficult to stain because the peptidoglycan layer is covalently attached to the polysaccharide arabinogalactan which lipids are esterified into making up 60% of the cell wall. Lipids are almost resistant to staining and to antibiotics and biocides.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What do peptidoglycan consist of?

A

repeating disaccharide units of 2 different N-acetylated amino sugars.
short peptide chains are attached to alternate amino sugars and these cross link via peptide bonds (cross links are species dependent)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Give 2 examples of enzymes that act on cell wall synthesis

A

transpeptidase and carboxypeptidase (they cleave the b lactic ring)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the three groups of beta lactic antibiotics?

A

penicillins, cephalosporins, carbapenems (all have a beta lactic ring)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What factors do beta lactams need to have in order to be effective?

A
  • must be able to penetrate the cell wall
  • should be resistant to beta lactamases (produced by bacteria causing resistance)
  • resistant to stomach acid (to ensure they don’t break down)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Give 3 examples of semi synthetic penicillins:

A

ampicillin (sensitive to B lactamase degradation), amoxicillin, methicillin and flucloxacillin (last 2 resistant to all B lacatmases which is good)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Why is penicillin given IV?

A

as it is acid labile

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are first, second and third generation cephalosporins?

A

1st: rarely used
2nd: gram -ve activity, given orally
3rd: gram -ve activity, IV, used for serious illness

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Give 2 examples of cephalosporins:

A

Cefaclor (2nd gen) and ceftriaxone (3rd gen)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are 2 advantages of carbapenems and give an example?

A
  • very broad spectrum
  • resistant to most beta lactamases
    e. g. imipenem
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are monobactams resistant against?

A

gram negative (only 1 monobactam - aztreonam)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is vancomycin?

A
  • non ribosomal peptide (very difficult to synthesise)
  • glycosolated with many unusual amino acids
  • inhibits cell wall synthesis by preventing cross link formation
  • given IV
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is vancomycin effective against?

A

gram positive only (can’t cross gram negative cell wall)

17
Q

What is an example of what vancomycin is used to treat?

A

Clostridium difficile infections - oral

18
Q

What is an alternative to vancomycin?

A

teicoplanin