Public: Beta Lactam antibiotics and Vancomycin Flashcards Preview

Pharmacy Year 2 Semester 1 > Public: Beta Lactam antibiotics and Vancomycin > Flashcards

Flashcards in Public: Beta Lactam antibiotics and Vancomycin Deck (30):
1

Give the bacterial cell wall function(s)

-Protects the cytoplasmic membrane from rupture, as the cell membrane is fragile and osmotic pressure inside of the cell is high.
-Maintains the shape of the cell

2

Describe the cell walls of norcardioform bacteria
e.g. M.tuberculosis

Gram positive but difficult to stain
peptidoglycan is covalently linked to the polysaccharide arabinogalactan
Lipids are esterified to arabinogalactan and make up 60% of the dry cell weight
Lipids confer resistance to staining, antibiotics and biocides

3

What is the major structural component of gram positive and gram negative cell walls?

Peptidoglycan

4

What does peptidoglycan consist of?

A repeating disaccharide unit of 2 different N-acetylated aminosugars
Short peptide chains are attached to alternate aminosugars and these crosslink to one another via peptide bonds.
Some bacteria have many sheets of peptidoglycan and these are joined by the same type of crosslink

5

Are the crosslinks between the polysaccharide chains are species dependent?

Yes

6

How are crosslinks in bacterial cell walls formed?

Crosslinks are formed by a transpeptidation reaction, catalysed by a membrae-bound transpeptidase.

7

Name one of a number of enzymes in the cell membrane that acts on cell wall synthesis.

carboxypeptidase

8

Name 3 types of beta lactam antibiotics

Penicillins
Cephalosporins
Carbapenems

9

Name 3 amino acids that are (somewhat) in penicillin

Valine

Cysteine

Phenylalanine

10

What factors control the activity and usefulness of beta lactam antibiotics?

-Ability to penetrate the cell wall
-Resistance to -lactamases
-Affinity of various Penicillin Binding Proteins
-Resistance to stomach acid
-Formulation, pharmacokinetics, toxicology etc.

11

Which penicillin was the original? What are the downfalls of using this?

Penicillin G
Acid labile therefore injection, sensitive to ß-lactamase degradation

12

Name 4 semi-synthetic penicillins

Ampicillin
Amoxicillin
Methicillin
Flucloxacillin

13

Ampicillin is better than penicillin in what way?
Any downfalls to it?

Acid-stable therefore oral route of administration
sensitive to beta-lactamase degradation

14

Amoxicillin is better than penicillin in what way?

resistant to class 1 beta-lactamase enzymes

15

Methicillin and Flucloaccilin are resistant to...

all beta-lactamases

16

Talk about cephlasporins structure and also the various different generations of them

Cephlasporin nucleus is biosynthesised in a similar way to the penicillin nucleus
Generation 1 - seldom used any more
Generation 2 - Have gram negative activity and are administered orally
Generation 3 - good gram negative activity and are useful against very serious illness. They are injected.

17

Give an example of a 2nd generation cephlasporin and what it is used to treat

Cefaclor
Gram negative activity and activity against Haemophilus

18

Give an example of a 3rd generation cephlasporin and what it is used to treat

Ceftriaxone
Given by intramuscular injection for serious infections, often in combination with a macrolide and an aminoglycoside

19

Describe advantages of carbapenems

Very broad spectrum
Resistant to most beta-lactamases

20

Monobactams?

Only one so far - Aztreonam
active against gram negatives only

21

Give an example of a carbapenem and describe its use

Imipenem
Rapidly deactivated by the kidneys unless administered with a certain inhibitor, Cilastatin

22

Describe the structure of Vancomycin

It's a non-ribosomal polypeptide
Made from many unusual amino acids
Glycosolated
Product of the soil microorganism Amycolatopsis orientalis

23

How does Vancomycin work?

Pushes apart crosslinks in the cell wall i.e. prevents cross link formation

24

Uses of vancomycin

Serious gram positive infections only (as it doesn't cross the gram negative cell wall)

25

Why is vancomycin normally injected?

Because the digestive system is designed to hydrolyse peptide bonds, of which vancomycin has many

26

What does oral vancomycin treat?

Clostridium diffcile infections

27

Describe the disagreement clinicians have regarding vancomycin use

Some commentators do not recommend vancomycin for treatment of MRSA, preferring nafcillin. However, injected rifampicin – vancomycin combination is preferred by many trusts.

28

3 reasons why vancomycin side effects may have been exaggerated

1) early preparations of vancomycin were very impure
2) People who reported nephrotoxicity were generally taking other nephrotoxins
3) Ototoxicity is rare

29

Name an alternative to vancomycin that is used

Teicoplanin
(another glycopeptide)
Mode of action believed to be very similar

30

When was vancomycin resistance first reported in the UK?

1999