Antimicrobial drugs tutorial Flashcards
What are the major differences between eukaryotic cells and prokaryotic cells?
Bacterial cells are anucleate, with no intracellular organelles and a substance called peptidoglycan in their cell wall.
What are the main targets for antibacterial chemotherapy?
- Their mode of replication
- Their biochemical pathways
- Their structural components
What group of drug are used to treat bacterial infections?
Antibiotics
What are the main differences that allow folate synthesis to be targeted for therapy?
Humans derive most of their folates from diet, bacterial cells must synthesise them. Also, the enzyme that processes folates is different in humans
Give examples of drugs that target folate metabolism.
Sulphonamides, trimethoprim
What differences allow bacterial protein synthesis to used as a target for chemotherapy?
a) Different form of DNA gyrase
b) Different form of RNA polymerase
c) Different ribosomes with different mode of action
Give examples of drug types that act on each of these targets.
a) The quinolones e.g. ciprofloxacin, cinoxacin
b) Rifampicin
c) Tetracyclines, chloramphenicol, aminoglycosides, macrolides, fusidic acid
Which antibiotic can become deposited with calcium in teeth causing staining?
Tetracycline
Which antibiotic can cause grey-baby syndrome?
Chloramphenicol
What substance in the bacterial cell wall can be used as a target for therapy?
Peptidoglycan
What is the type of antibiotic that acts to inhibit its synthesis?
β-lactams
Which antibiotics act on the plasma membrane and how do they work?
Polymixins
Act like detergents to disrupt phospholipids in membrane
Why are viruses the ultimate parasites?
Must hijack host cells for survival.
Give examples of DNA viruses.
- Poxviruses – smallpox
- Herpesviruses - chickenpox, shingles, cold sores, glandular fever
- Adenoviruses -sore throat, conjunctivitis
- Papillomaviruses - warts
Give examples of RNA viruses.
- Orthomyxoviruses – influenza
- Paramyxoviruses - measles, mumps
- Rubella virus - German measles
- Rhabdoviruses – rabies
- Picornaviruses – colds, meningitis, poliomyelitis
What are retroviruses?
Virion contains RNA and a reverse transcriptase (viral RNA-dependent DNA polymerase) i.e. makes DNA from RNA
How does acyclovir work?
Inhibits herpesvirus DNA polymerase
How does AZT work?
Inhibits viral RNA reverse transcriptase, is a thymine nucleoside analogue
How do virus specific protease inhibitors work?
These prevent the inactive viral polyprotein from becoming activated.
What type of drugs are used to treat fungal infections?
Antimycotics
Which drug is used mainly to treat nail infections and how does it work?
Griseofulvin – inhibits fungal mitosis
How do the azoles work? Give an example.
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
How do the allyamines work? Give an example.
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
How does flucytosine work?
Converted to active metabolite 5-fluorouracil and incorporated into RNA so inhibiting protein synthesis, also disrupts DNA synthesis
How does echinocandin work?
Inhibit synthesis of glucan in the fungal cell wall
Non-competitive inhibitors of 1,3 β glucan synthase
