Antimicrobial drugs tutorial

Question 1

What are the major differences between eukaryotic cells and prokaryotic cells?

Answer 1

Bacterial cells are anucleate, with no intracellular organelles and a substance called peptidoglycan in their cell wall.

Question 2

What are the main targets for antibacterial chemotherapy?

Answer 2

• Their mode of replication
• Their biochemical pathways
• Their structural components

Question 3

What group of drug are used to treat bacterial infections?

Answer 3

Antibiotics

Question 4

What are the main differences that allow folate synthesis to be targeted for therapy?

Answer 4

Humans derive most of their folates from diet, bacterial cells must synthesise them. Also, the enzyme that processes folates is different in humans

Question 5

Give examples of drugs that target folate metabolism.

Answer 5

Sulphonamides, trimethoprim

Question 6

What differences allow bacterial protein synthesis to used as a target for chemotherapy?

Answer 6

a) Different form of DNA gyrase
b) Different form of RNA polymerase
c) Different ribosomes with different mode of action

Question 7

Give examples of drug types that act on each of these targets.

Answer 7

a) The quinolones e.g. ciprofloxacin, cinoxacin
b) Rifampicin
c) Tetracyclines, chloramphenicol, aminoglycosides, macrolides, fusidic acid

Question 8

Which antibiotic can become deposited with calcium in teeth causing staining?

Answer 8

Tetracycline

Question 9

Which antibiotic can cause grey-baby syndrome?

Answer 9

Chloramphenicol

Question 10

What substance in the bacterial cell wall can be used as a target for therapy?

Answer 10

Peptidoglycan

Question 11

What is the type of antibiotic that acts to inhibit its synthesis?

Answer 11

β-lactams

Question 12

Which antibiotics act on the plasma membrane and how do they work?

Answer 12

Polymixins
Act like detergents to disrupt phospholipids in membrane

Question 13

Why are viruses the ultimate parasites?

Answer 13

Must hijack host cells for survival.

Question 14

Give examples of DNA viruses.

Answer 14

• Poxviruses – smallpox
• Herpesviruses - chickenpox, shingles, cold sores, glandular fever
• Adenoviruses -sore throat, conjunctivitis
• Papillomaviruses - warts

Question 15

Give examples of RNA viruses.

Answer 15

• Orthomyxoviruses – influenza
• Paramyxoviruses - measles, mumps
• Rubella virus - German measles
• Rhabdoviruses – rabies
• Picornaviruses – colds, meningitis, poliomyelitis

Question 16

What are retroviruses?

Answer 16

Virion contains RNA and a reverse transcriptase (viral RNA-dependent DNA polymerase) i.e. makes DNA from RNA

Question 17

How does acyclovir work?

Answer 17

Inhibits herpesvirus DNA polymerase

Question 18

How does AZT work?

Answer 18

Inhibits viral RNA reverse transcriptase, is a thymine nucleoside analogue

Question 19

How do virus specific protease inhibitors work?

Answer 19

These prevent the inactive viral polyprotein from becoming activated.

Question 20

What type of drugs are used to treat fungal infections?

Answer 20

Antimycotics

Question 21

Which drug is used mainly to treat nail infections and how does it work?

Answer 21

Griseofulvin – inhibits fungal mitosis

Question 22

How do the azoles work? Give an example.

Answer 22

Bind to iron core of haem group in fungal cytochrome P450 enzymes (involved in ergosterol synthesis) and so impairs cell membrane function, e.g. ketoconazole

Question 23

How do the allyamines work? Give an example.

Answer 23

Inhibit the enzyme squalene 2,3-epoxidase which is involved in ergosterol synthesis. Results in accumulation of squalene concentration in the cell wall and so fungal death, e.g. terbinafine

Question 24

How does flucytosine work?

Answer 24

Converted to active metabolite 5-fluorouracil and incorporated into RNA so inhibiting protein synthesis, also disrupts DNA synthesis

Question 25

How does echinocandin work?

Answer 25

Inhibit synthesis of glucan in the fungal cell wall
Non-competitive inhibitors of 1,3 β glucan synthase