7. Antibiotics (Mode of Action)

Question 1

Functions of antibiotics (2)

Answer 1

Break down gram-positive and gram-negative cell walls

Reduce competition for nutrients and space

Question 2

Microbial growth control (2)

Answer 2

Physical

Chemical

Question 3

Types of physical microbial growth control (2)

Answer 3

Heat sterilisation

Radiation sterilisation

Question 4

Types of chemical microbial growth control (3)

Answer 4

Antiseptics (biological) and disinfectants (inanimate)
Natural antimicrobials
Synthetic antimicrobials

Question 5

Definition of antibiotics (3)

Answer 5

Chemical substance produced by one organism that is destructive to another
Naturally occurring antimicrobials
Metabolic products of bacteria and fungi

Question 6

Types of antibiotics (2)

Answer 6

Bacteriostatic
Bactericidal (better)

Question 7

Cellular targets of antibiotics (4)

Answer 7

Cell wall
Cell membrane
Nucleic acid
Protein synthesis

Question 8

Ideal antimicrobial agent features (8)

Answer 8

Selective toxicity against microbial target
Minimal toxicity to host
Cidal activity (kills micro-organisms)
Long plasma half-life
Good tissue distribution
Low binding to plasma proteins
Oral and parenteral preparations
No adverse interactions with other drugs

Question 9

Antimicrobial targets/function (5)

Answer 9

Inhibition of cell wall synthesis
Inhibition of protein synthesis
Inhibition of nucleic acid replication and transcription
Injury to plasma membrane
Inhibition of synthesis of essential metabolites

Question 10

Antimicrobials that inhibit cell wall synthesis (4)

Answer 10

Penicillins
Cephalosporins
Bacitracin
Vancomycin

Question 11

Antimicrobials that inhibit protein synthesis (4)

Answer 11

Chloramphenicol
Erythromycin
Tetracyclines
Streptomycin

Question 12

Antimicrobials that inhibit nucleic acid replication and transcription (2)

Answer 12

Quinolones

Rifampin

Question 13

Antimicrobials that injure plasma membrane

Answer 13

Polymyxin B

Question 14

Antimicrobials that inhibit synthesis of essential metabolites (2)

Answer 14

Sulphanilamide

Trimethoprim

Question 15

How does antibiotic resistance develop

Answer 15

From misuse of antibiotics selected for resistant mutants

Question 16

Examples of antibiotic misuse (5)

Answer 16

Using outdated or weakened antibiotics
Using antibiotics for a cold and other inappropriate conditions (viruses)
Using antibiotics in animal feed
Failing to complete prescribed antibiotic regiment
Using someone else’s (leftover) prescription