Antibiotics

Question 1

bactericidal

Answer 1

Kill

Question 2

Bacteriostatic

Answer 2

slow/stop replication

Question 3

Ideal Antibiotic

Answer 3

• broad spectrum
• not induce resistance
• high therapeutic index
• –ratio of 1 means effective dose would be toxic
• selective toxicity

Question 4

Selective Toxity

Answer 4

Cell wall is unique in microbes
Enzymes for replicaiton, transcription, and translation can be unique in microbes
Microbes have some unique essential metabolites
Ribosome structure unique in microbes

Question 5

Penicillin

Answer 5

Disrupts cell wall synthesis

• cleaves off D-ala needed for synthesis
• after cleavage becomes toxic for bacterial cell

Question 6

Inhibition of DNA replication problem

Answer 6

these inhibitors can attach to host dna

• metronidazole is inactive in aerobic conditons
• -only becomes active in anaerobic bacterial conditions

Question 7

DNA gyrase

Answer 7

unique in bacteria

-attacked by nalidixic acid and quinolones

Question 8

rifamycin

Answer 8

inhibit RNA polymerase

Question 9

Steps in the action of antibiotics

Answer 9

1. Drug penetrates the envelope
2. Transport into the cell
3. Drug binds to target

Question 10

Mechanism of Drug Resistance

Answer 10

Synthesis of enzymes that inactivate the drug

Prevention of access to the target site

1. Inhibiting uptake
2. Increasing secretion of the drug

Modification of the target site

Question 11

Preventing access to target site

Answer 11

Many antibiotics enter the cell through porins (proteins that extend across the lipid bilayer and create channels or pores)
Resistance to tetracyclines and quinolones
Some bacteria develop efflux pumps to pump the antibiotics out of them (resistance to tetracycline)
All classes of bacteria have been shown to have drug efflux transporters

Question 12

Modification of target site

Answer 12

1. Modify enzyme affinity

2. Alteration of metabolic pathway