Antimicrobials

Question 1

Why does a larger therapeutic index make for a safer drug?

Answer 1

Greater difference between point of therapeutic benefit to the pt and the point where the drug becomes toxic.

Question 2

What characteristics should an Ab have?

Answer 2

Wide spectrum 
Non-toxic and no undesirable side effects
Non-allergenic
Shouldn't kill host's flora
Able to reach infection site
Cheap and easy to produce
Long shelf life (chemically stable)
Microbial resistance unlikely to develop against it

Question 3

How do Beta-lactam Ab work? Give an example.

Answer 3

Inhib bacteria growth by stopping peptidoglycan cell wall formation (bactericidal) - penicillin.

Question 4

Some Ab block peptidoglycan formation (B-lactams, Glycopeptides, Cycloserines). What crosslinks peptidoglycan layers?

Answer 4

D-alanine

Question 5

Why are aminoglycosides not effective against anaerobes?

Answer 5

Bact uptake requires O2

Question 6

Tetracyclines

Answer 6

Bacteriostatic (stop bact formation by stopping tRNA binding to mRNA)
Broad spectrum
Incorperated into developing bones and teeth
Widespread resistance

Question 7

Antibiotic resistance

Answer 7

an organism that is not inhibited or killed by an antibacterial agent at concentrations of the drug achievable in the body after normal dosage

Question 8

Transposons

Answer 8

Carry resistance genes and jump between chromosome and plasmid

Question 9

Causes of Ab resistance?

Answer 9

Mutation - lower affinity to Ab
Target overproduced 
Drug not activated
Drug removed (enzymes destroy)
Drug cannot enter cell

Question 10

3 ways antivirals can work?

Answer 10

Prevent fusion of virus w cell memb
Stop DNA synthesis at transcription and translation stages
Post translational inhibition - protease inhibitors