Antibiotics Flashcards
Define selective toxicity
when the Abx will only affect the target organism w/o harming the host (mild toxicity of host and side effects are ok )
What are the 6 primary sites of actions of Abx on bacterial cells
- Cell wall 2. 50 S subunit of ribosome 3. 30 S subunit of ribosome 4. Cell membrane 5. DNA 6 Metabolism
What are the Abx that target bacterial cell walls
- Beta lactams 2. Vancomycin 3. Bacitracin 4. Monobactams
What are the 2 classes of beta lactams
- Penicillins 2. Cephalosporins
What does a bet lactam ring look like
What happens when you change the side changes of a beta-lactam ring
the abx properties can be changed
What is the principle of action of beta lactams
inhibits peptidoglycan synthesis at penicillin binding proteins, by inhibiting formation of cross links between NAM and NAG
What are the major characteristics of beta lactams
- bactericidial
- low toxicity
- most effective against gram positive bacteria
- only effective against activelygrowing bacteria
What is the mode of action for Vancomycin
Binds to cross link peptide of NAM/NAG so that the link cannot be completed the polymer cannot be elongated
What is the mode of action for Bacitracin
Blocks the phosolipid carrier that helps carries subunits of peptidoglycan across the cell membrane to the cell wall
-not beta lactam
What is Isoniazid
Abx that blocks the formation of mycolic acid in mycobacterium (TB) cell walls
What are the 4 class of Abx that work on the 50S subunit of bacterial ribosomes
- Chlorampheniol
- Clindamycin
- Linezolid
- erythromycin/Macrolides
What is the mode of action for Chlorampheniol and Clindamycin
inhibits polypeptide elongation by inhibiting peptide bond formation
True or False Chlorampheniol and Clindamycin are bactercidal
False, they are bacteristatic
-think of their mechanism
True or False Chlorampheniol and Clindamycin board spectrum Abx
True, think of their mschanism
What is the mode of action for macrolides
binds to 50S ribosomal subunit and prevents translocation of mRNA
What is a type of macrolide
erythromycin
What are the 3 classes of Abx that work on the 30S bacterial ribosomal subunit
- Streptomycn
2 . Aminoglycosides
3 Tetracyline
What is the mode of action of Aminoglycosides
inhibt translation by causing misreading of mRNA at 30s ribosomal subunit
How does resistance occur in beta-lactams
- entrance of Abx is not allowed into bacteria
- Chnage in PBP structure so Abx cannot bind
- Beta-lactamases hydrolysize the Abx
What is the mode of action of Tetracyclines
Blocks tRNA from binding to 30S mRNA complex
Are the 30S abx board or narrow spectrum
Board, think mech of action
How is resistance acheived against aminoglycosides
enzymatic modifiction of Abx
How is resistance acheived against Tetracylines
efflux of Abx out of the cell by bacteria
What is the mode of action of Polymixins
disrupts fxnal integrity of cytoplasmic membrane
Where are polymixins used and why
external use only, because they are nephrotoxic
True or False polymixins are affective against gram positive bacteria
False, they are only affect against gram negatives
What is the mode of action of Amphotericin B
antifungal, binds ergosterol in fungal membranes disrupting them
What are the classes of Abx that inhibit nucleic acid synthesis and modes of action ?
- Quinolones=Blocks DNA gyrase
- Rifampin = Bloock RNA polermerase
- Metronidazole =Breaks DNA bonds
True or False, nuleoside analogues are antivirals
True
What is an example of a viral nuceloside analogue
Acyclovir
What class of Abx inhibits bacterial metabolism
- Sulfonamides
- Trimethoprim
They both work by interfering with folic acid synthesis
What is the mechanism of action for Azoles
inhibit synthesis of ergosterol in fungal cells
What are the points of antiviral action
- Block attachement and entry
- Blocking release of genome from viral capsid (uncoating)
- Inhibit replication of viral genome
- Inhibit protein
