Bacteria III

Question 1

What links the glycan strands together?

Answer 1

Peptide bonds

Question 2

What are the targets in peptidoglycan synthesis?

Answer 2

Transglycosylation and transpeptidation

Question 3

What does transglycosylation do?

Answer 3

Polymerises the glycan strands

Question 4

What does transpeptidation do?

Answer 4

Cross links between glycan strands

Question 5

What catalyses transpeptidation and transglycosylation?

Answer 5

Penicillin binding proteins

Question 6

What are the two main agents that interfere with bacterial wall synthesis?

Answer 6

Beta lactams and glycopeptides

Question 7

What do beta lactams block?

Answer 7

Penicillin binding proteins - block cross-link of the peptide side chains

Question 8

Are peptidoglycan hydrolyses affected by beta lactams?

Answer 8

No - they continue to hydrolyse PG & this leads to weakening of peptidoglycan especially at the division site. Leads to protrusion of cytoplasmic membrane and osmotic lysis/cell death.

Question 9

What can occur after beta lactam injection?

Answer 9

Anaphylactic shock

Question 10

What do beta lactamases do?

Answer 10

Break down and remove the structural analogity of beta lactams
Have a serine in their AS responsible for catalysis
Zinc have a broader spectrum than serine

Question 11

What can inhibit beta lactamases?

Answer 11

Clavulin

Question 12

What is the core structure of penicillin?

Answer 12

6-aminopenicillianic acid - can modify the chemical group to make a range of molecules

Question 13

What does the nature of the R group determine?

Answer 13

The drugs stability to enzymatic or acidic hydrolysis and affects its antibacterial spectrum

Question 14

What are the four types of beta lactam?

Answer 14

Penicillins
Cephalosporins - broad spectrum (4th), found in urine, can penetrate into the CSF
Carbapenems
Monobactams

Question 15

What are the three types of carbapenem?

Answer 15

Imipenem
Meropenem 
Ertapenem
Very stable to most serine beta lactamases 
Kept in reserve

Question 16

What does vancomycin bind to?

Answer 16

D-ala-D-ala and blocks the subsequent reactions that would take place. Inhibitor of transglycosylation
Can’t penetrate into Gram negative as it is too big for the channels

Question 17

What does vancomycin treat?

Answer 17

S.Aureus particularly MRSA

Patients that are hypersensitive to penicillin

Question 18

What targets the membrane?

Answer 18

Polymyxin & colistin - active against gram negative bacteria

Question 19

What part of the membrane do polymyxin and colistin target?

Answer 19

Lipopolysaccahrides and cause disruption of the IM membrane

Can be used as therapy for cystic fibrosis infections

Question 20

What is daptomycin?

Answer 20

Targets the membrane and is a cyclic lipopeptide - doesn’t make specific contacts with the lipopolysaccahrides

Question 21

What does daptomycin need to be present to work?

Answer 21

Calcium ions as you need to stop the repulsion

Question 22

What can daptomycin be used to treat?

Answer 22

Complicated skin/soft tissue infections

Question 23

How is daptomycin administered?

Answer 23

IV

Question 24

What are the adverse side effects of daptomycin?

Answer 24

Muscle toxicity

Question 25

What are the strands in peptidoglycan?

Answer 25

NAM and NAG