Lecture 16 and 17 - Antibiotics

Question 1

What is an antibiotic?

Answer 1

An antibiotic is a pharmaceutical agent that is specifically used to treat bacterial infections. It can be bactericidal or bacteriostatic. Meaning it either kills or prevents reproduction respectively.

Question 2

Define selective toxicity. Give example

Answer 2

The ability of an agent to target the bacterium with minimal toxic effect to the host.

Question 3

List the different types of antibiotic used to treat microbial infection

Answer 3

Cell wall inhibitors i.e. B-Lactams and cephalosporins, protein synthesis inhibitors ie. Tetracyclines and Folic acid metabolism inhibitors such as Sulfonamides.

Question 4

What is the mode of action of B-lactam antibiotics?

Answer 4

Penicillin binding proteins (PBP) are responsible for cross linking NAM and NAG to create the cell wall. Beta Lactam antibiotic prevent PBP such as transpeptidase and carboxypeptidase from achieving this. Thereby B-lactams are bacteriostatic.

Question 5

How does bacteria build resistance to antibiotics? What are some new antibiotics used to treat such bacteria?

Answer 5

Bacteria build resistances through several ways some include: Decreased permeability: where porins are altered therefore drugs cannot enter, active efflux: diminished intracellular concentration of drugs where it is pumped out. Overproduction of target can also occur where there can be an increased expression of PBPs.

Clavulanic acid (B-lactamase inhibtor) + amox

Question 6

What is the mechanism of action of macrolides?

Answer 6

Macrolides are protein synthesis inhibitors that inhibit the P site of the 50S. They contain a lactone ring. It prevents peptide chain elongation therefore inhibiting protein synthesis.

Question 7

What is the mode of actions of tetracyclines?

Answer 7

Tetracycline is a bacteriostatic drug that acts by binding reversibly to the 30S subunit of the bacterial ribosome.

Question 8

What is the mode of actions of aminoglycosides?

Answer 8

Aminoglycosides such as streptomycin is used to treat tuberculosis, it binds to the 30S subunit of the ribosomes it can be extremely toxic to host and is usually left for extreme situations.

Question 9

How can we measure an antibiotics effectiveness?

Answer 9

Through disc diffusion test and sensitivity testing

Question 10

What is the mode of action of aminoglycosides?

Answer 10

Aminoglycosides are protein synthesis inhibitors that binds reversible to the 30s (large) ribosomal unit