chapter 26 (3)

Question 1

Naturally occurring antimicrobial drugs: Antibiotics

Answer 1

Antibiotics are naturally produced antimicrobial agents

• Less than 1% of known antibiotics are useful.
• Can be modified to enhance efficacy.

Question 2

Naturally occurring antimicrobial drugs: Susceptibility of microbes to different antibiotics

Answer 2

• Gram + and gram - bacteria vary in their sensitivity to antibiotics.
• Broad spectrum antibiotics effective against both groups of bacteria.

Question 3

Targets of antibiotics

Answer 3

Cell wall. 
Cytoplasmic membrane. 
Lipid biosynthesis enzymes. 
DNA replication. 
Transcription. 
Ribosomes.

Question 4

B-Lactam antibiotics: Penicillins and Cephalosporins

Answer 4

B-lactam antibiotics are one of the most important groups of antibiotics.

• Penicillins and Cephalosporins
• Over half of all antibiotics used worldwide.

Question 5

Penicillins

Answer 5

Discovered by Alexander Fleming (1928).
Primarily effective against gram+ bacteria.
Some synthetic forms are effective against Gram- bacteria.
Target call wall synthesis.

Question 6

Cephalosporins

Answer 6

Produced by fungus cephalosporium
Same mode of action as penicillins.
Commonly used to treat gonorrhea.

Question 7

Beta-lactams

Answer 7

Only work on replicating cells. 
4-membered B-lactam ring. 
Include:
-penicillin
-Cephalosporons 
-Carbapenems
-Monobactams
Problems:
-allergic rxn

Question 8

Beta-lactam: Process

Answer 8

Inhibiting last step in peptidoglycan synthesis.
Triggers endogenous enzymes to degrade peptidoglycan.
Destruction of peptidoglycan results in loss of cell wall and bacterial lysis.

Question 9

Glycopeptides

Answer 9

Ex:
-vanomycin
Inhibits transglycosylation & transpepidation of peptidoglycan synthesis.
Effective against Gram+ bacteria only.

Question 10

Phosphonomycin & Bacitracin

Answer 10

Inhibit peptidoglycan by inhibiting earlier steps in peptidoglycan biosynthesis.
Phosphonomycin: inhibits conversion of UDP-NAG to UDP-NAM. (MRSA).
Bacitracin inhibits the recycling of bactoprenol.
Only used topically, too toxic for internal use.