Antibacterials

Question 1

What do class I reactions in bacteria produce?

Answer 1

Precursor molecules & ATP

Question 2

What do class II reactions in bacteria produce?

Answer 2

Hexosamines, amino acids & nucleotides

Question 3

What do class III reactions in bacteria produce?

Answer 3

Peptidoglycan, proteins, RNA & DNA

Question 4

What are the major targets for antibacterial drugs?

Answer 4

• DNA gyrase
• DNA-directed RNA polymerase
• Cell-wall synthesis
• Folic acid metabolism
• Oxazolidinones
• Protein synthesis
• 50s & 30s ribosomes

Question 5

Which class of bacteria are more sensitive to penicillins?

Answer 5

Gram +Ve
gram -ve
- lipopolysaccharide layer which prevents penicillins getting to the site of action

Question 6

What is the action of beta-lactams in terms of inhibiting peptidoglycan?

Answer 6

Prevent the cross-linking peptides from binding to the tetrapeptide side-chains

Question 7

What is the antibacterial activity of Beta-lactams?

Answer 7

Have an ability to bind penicillin binding proteins to inhibit transpeptidases

Question 8

What is the antibacterial activity of Beta-lactams?

Answer 8

Have an ability to bind penicillin binding proteins to inhibit transpeptidases

Question 9

How can resistance to beta-lactams develop?

Answer 9

Mutations in transpeptidases & beta-lactamase activity

Question 10

What is the action of clavulanic acid?

Answer 10

Beta-lactamase inhibitor, no antibacterial effect alone

Question 11

What is benzylpenicillin most effective against?

Answer 11

Gram positive bacteria & cocci

Question 12

Why can benzylpenicillin not be administered orally?

Answer 12

Is acid instable so will be broken down in stomach

Question 13

What is the acid stability of ampicillin?

Answer 13

Medium

Question 14

What is the acid stability of amoxicillin?

Answer 14

Very good

Question 15

What is the beta-lactamase stability of ampicillin and amoxicillin?

Answer 15

Susceptible

Question 16

What is the spectrum of ampicillin and amoxicillin?

Answer 16

G+ cocci and G-

Question 17

Which antibacterials compete with tRNA for the A site?

Answer 17

Tetracyclines

Question 18

Which antibacterials inhibit peptide bond formation?

Answer 18

Chloramphenicol and florfenicol

Question 19

Which antibacterials inhibit translocation?

Answer 19

Macrolides

Question 20

How do sulphonamides & trimethoprim target bacteria?

Answer 20

Inhibit bacterial folate synthesis

Question 21

What enzyme do sulphonamides target?

Answer 21

Dihyrdropteroate synthetase

Question 22

What enzyme does trimethoprim inhibit?

Answer 22

dihydrofolate reductase

Question 23

What are the biochemical mechanisms of antibiotic resistance?

Answer 23

• Inactivation of the antibacterial drug
• Alteration of the target site
• Decrease drug accumulation in the bacterium
• Upregulate synthesis of target
• Alter metabolic pathway of bacteria

Question 24

What will happen if the gene for beta-lactamase is encoded on a bacterial chromosome and how is it different to a plasmid?

Answer 24

Chromasomal - Expression inducible, won’t produce beta-lactamase until exposed to the drug
Plasmids - constitutively produced

Question 25

How can drug binding sites be altered?

Answer 25

• Mutations in proteins
• erythromycin resistance - mutation in 50S subunit
• Quinolones - mutation in DNA gyrase

Question 26

What do efflux pumps do?

Answer 26

method of decreasing drug accumulation - remove the tetracyline from the bacterium so it cant inhibit protein synthesis