Antibiotics

Question 1

Modes of action of antibiotics

Answer 1

bacteriocidal: kill bacteria
bacteriostatic: prevent replication and slow activity

Question 2

traits of an ideal antibiotic

Answer 2

1. broad spectrum of activity
2. does not induce resistance
3. high therapeutic index (ratio between toxic dose and effective dose)
4. selective toxicity

Question 3

What characteristics of bacteria can be targeted to achieve selective toxicity?

Answer 3

1. unique cell wall
2. enzymes from replication, transcription and translation
3. microbes have some unique essential metabolites
4. ribosome structure is unique in some microbes

Question 4

5 pathways antibiotics attack

Answer 4

1. inhibit cell wall synthesis - penicillin
2. disruption of cell membrane function - polymyxin
3. inhibition of protein synthesis - erythromycin, streptomycin
4. act as an antimetabolite - sulfonamide (inhibit folic acid usage)
5. inhibition of nucleic acid synthesis - quinolones, rifamycin, metronizidale

Question 5

What are the steps of antibiotic action?

Answer 5

1. drug penetrates the envelope
2. drug is transported into cell
3. drug binds to target

Question 6

mechanisms of drug resistance

Answer 6

1. synthesis of enzymes that inactivate the drug
2. prevention of access to the target site
3. modification of target site

Question 7

How can drug resistance spread?

Answer 7

1. chromosome associated resistance (to next generation)
2. Plasmid mediated resistance
3. rapid spread of resistance