Antibiotics

Question 1

What are the 5 types of antibiotics?

Answer 1

Cell wall synthesis inhibitors.
Cell membrane integrity interruptors.
Metabolic pathway inhibitors.
Nucleic acid synthesis inhibitors.
Protein synthesis inhibitors.

Question 2

What do beta lactams do?

Answer 2

Act as a blocker of the transpeptidase enzymes by imitating a a reactant and ‘locking’ the enzyme. The biosynthesis of the peptidoglycan is mediated by transpeptidase enzymes. These catalyse the terminal lysine/alanine reaction

Question 3

What are 4 examples of beta lactams?

Answer 3

Penicillins, cephalosporins, carbapenams, monobactams

Question 4

What are examples of cell membrane integrity disruptors? What gram type of bacteria are the examples useful against?

Answer 4

Daptomycin- Works by forming a complex with calcium and facilitates its insertion into the cell wall. These pores allow potassium to leak through. Gram positive
Polymixins- Binds to LPS in the outer membrane causing structural changes that increase membrane permeability. This allows disruption of the inner membrane. Gram negative.

Question 5

What are examples of nucleic acid synthesis inhibitors? How do they work?

Answer 5

Metronidazole- Diffuses across the cell membrane of anaerobic bacteria and is converted by pyruvate ferrodoxin oxidoreductase. This forms a nitryl radical anion.
Quinolones- Inhibit DNA gyrase and topoisomerase IV
Rifamycins- Inhibit RNA polymerase

Question 6

What are examples of protein synthesis inhibitors? How do they work?

Answer 6

30s Subunit inhibitors- aminoglycosides (gentamycin), tetracyclines (block entry of amino acyl tRNA molecules into the A site of the ribosome
50s subunit inhibitors- amphenicols (block peptide bond formation, macrolides (erythromycin- block the peptide exit tunnel that the newly assembled polypeptides pass through on their way to the cytoplasm)

Question 7

What are examples of metabolic pathway inhibitors? How do they work?

Answer 7

Trimethoprim targets the folic acid pathway by inhibiting DHFR