Antiobiotic Action

Question 1

Define antimicrobials/antibiotic
-2 types

Answer 1

Agents that kills microorganisms or stops their growth
2 types:
-antibiotic- microbial origin (commonly made by a bacteria)
-antimicrobial- chemically synthesised

Question 2

Selective toxicity meaning
-how do bacteria exert selective toxicity

Answer 2

kill or inhibit the infecting organism without damaging the host
-targets something unique to bacteria e.g peptidoglycan of cell wall

Question 3

2 types of actions of antimicrobials

Answer 3

Bactericidal
-kills bacteria
-is irreversible
-may or may not cause lyses of bacteria

Bacteriostatic
-suppresses bacteria but doesn’t kill it
-reversible

Question 4

What are the sites of action of main antibiotics

Answer 4

Cell wall
Plasma membrane
Ribosomes
DNA synthesis
Metabolic pathways

Question 5

Best target for selective toxicity

Answer 5

Cell wall

Question 6

Peptidoglycan is made up of 2 components:

Answer 6

N-acetylglucosamine (NAG)
N-acetylmuramic (NAM)

Question 7

Basic subunits of petidoglycan

Answer 7

NAG, NAM, peptide connected together

Question 8

Describe process of biosynthesis of peptidoglycan

Answer 8

1.Subunit of peptidoglycan made in cytoplasm
2.Transported across cell membrane
3.Once in cell wall added to growing peptidoglycan chain
4.Strength and rigidity of structure provided by cross links of peptide bonds

Question 9

Name antibiotics which inhibit each step of biosynthesis of peptidoglycan

Answer 9

1.Subunit of peptidoglycan made in cytoplasm—> cycloserine, fosfomycin
2.Transported across cell membrane—> bacitracin
3.Once in cell wall added to growing peptidoglycan chain —> glycopeptides
4.Strength and rigidity of structure provided by cross links of peptide bonds—> beta-lactams e.g penicillin (most important group)

Question 10

4 types of beta-lactams antibiotics

Answer 10

Penicillin
Cephalosporin
Monobactam
Carbapenem

Question 11

What do all b-lactams have in common?

Answer 11

All have a b-lactam ring (square shaped ring with double bonded oxygen and single bond nitrogen)

Question 12

Which of the b-lactam antibiotics is only used in humans- shouldn’t be used in animals

Answer 12

Cephalosporin

Question 13

B-lactam antibiotics only work on what kind of bacteria?

Answer 13

Growing bacteria

Question 14

Steps of bacterial replication

Answer 14

-Bacterial cells chromosome replicates and cell elongates (stretches)
-chromosome separates and cytoplasmic membrane and cell wall invaginates
-cross wall formation complete
-daughter cells separate

Question 15

How does b-lactam antibiotic work

Answer 15

For elongation of bacteria (during bacterial replication), it must make breaks in the peptidoglycan in order to add more peptidoglycan. Whilst it’s doing that peptidoglycan is weak, causing water to enter the cell which drives the elongation of bacteria. However this breakage in cell allows for b-lactam inhibition

Question 16

Microscopic effect of b-lactam on bacteria

Answer 16

Normal Bacteria—> Cell growth—> bulging of cell—> lysis of cell

Question 17

Name the protein synthesis inhibitors (PSIs)

Answer 17

Aminoglycosides
Chloramphenicol
Macrolides & Lincosamides
Tetracyclines

Question 18

Protein synthesis inhibitors (PSI): Aminoglycosides
-what does it do

Answer 18

Inhibits initiation of bacterial protein synthesis
Causes misreading of mRNA

Question 19

Proetin synthesis inhibitors: Chloramphenicol, macrolides and lincosamides
-function

Answer 19

-All inhibit peptidoglycan transferase which transfers the amino acid from tRNA P site to A site during translation
-macrolides & lincosamides: inhibit translation of ribosome along mRNA

Question 20

Protein synthesis inhibitor: tetracyclines

Answer 20

Bind to A site and prevent binding of tRNA coming with amino acid

Question 21

Bacteria DNA must be tightly wound inside cell. Which enzymes activate the super coiling and Which antibiotics inhibit this super coiling of DNA

Answer 21

Topoisomerase II activates
Quinolones and 4-fluoroquinolones inhibit

Question 22

Antibiotic which disrupts gram negative bacterial membrane
-properties

Answer 22

Polymixins
-cyclic peptide, not made of ribosomes
-have a free fatty acid residue which acts like a detergent
-disrupt cytoplasmic membrane
-very toxic so not used when possible

Question 23

Antibiotic which disrupts gram positive bacterial membrane
-causes what

Answer 23

Daptomycin
-causes loss of ions from interior of bacteria

Question 24

3 types of interaction of antibiotics

Answer 24

Synergism- 2 o more drugs work together fora better effect against bacteria
Antagonism- drugs working together causes a worse effect on bacteria (want to avoid this one)
Indifference- drugs working together doesn’t make a difference