Principles of antimicrobial chemotherapy

Question 1

What is microbial chemotherapy?

Answer 1

the use of chemicals to inhibit the growth and replication of invading organisms

Question 2

What is selective toxicity?

Answer 2

drugs intended to be toxic to the invading organism but relatively harmless to the host or normal cells

Question 3

What does selective toxicity depend on?

Answer 3

the existence of biochemical differences between the target group of cells and the host

Question 4

What are the main classes of antibacterial agent?

Answer 4

aminoglycosides 
penicillins 
cephalosporins 
bacterial folate antagonists 
tetracyclines 
fluoroquinolones 
erythromycin, clindamycin

Question 5

What are peptidoglycans?

Answer 5

• made up of amino sugars
• make up the cell wall of bacteria
• do not occur in eukaryotes
  crosslinking gives cell strength

Question 6

How do aminoglycosides work?

Answer 6

• form ionic bonds at cell surface
• penetrate cell wall
• diffuse into cytoplasm and bind to bacterial ribosomes

Question 7

How do penicilin and cephalosporins work?

Answer 7

specifically inhibits the enzyme that catalyses the final step in cell wall biosynthesis

Question 8

How do bacterial folate antagonists work?

Answer 8

through the inhibition of the folate pathway of bacteria

Question 9

How do tetracyclines work?

Answer 9

prevents attachment of tRNA to acceptor site on the mRNA-ribosomal complex and so prevents attachment of amino acid to peptide chain

Question 10

How do fluoroquinolones work?

Answer 10

by inhibiting DNA gyrase which prevents transcription and replication

Question 11

How do erythromycin and clindamycin work?

Answer 11

• prevent the addition of amino acids to the growing peptide chain by binding to ribosomes
• prevents ribosomes translocating down the mRNA template