Intro to antimicrobial chemotherapy

Question 1

list the mechanism of action of antibacterial drugs

Answer 1

inhibit cell wall synthesis
inhibit protein synthesis
inhibit DNA replication
inhibit metabolism

Question 2

list the mechanism of action of antifungal drugs

Answer 2

inhibit cell wall synthesis
alter cell membrane integrity or permeability
* inhibit mitosis
* inhibit DNA synthesis

Question 3

list the mechanism of action of anti-HIV drugs

Answer 3

• entry inhibitors
• reverse transcriptase inhibitors
• integrase inhibitors
• protease inhibitors

Question 4

explain the difference in action between -cidal and -static antimicrobial drugs

Answer 4

• -cidal - lethal to organism and kills microbes
• -static - slow down microbial growth by blocking replication

Question 5

explain the difference in action between broad-spectrum and narrow-spectrum antimicrobial
drugs

Answer 5

• broad spectrum - drugs are effective against a wide range of species
• narrow spectrum - drugs are effective against specific species

Question 6

explain the principle of broth microdilution to determine the minimum inhibitory concentration

Answer 6

Bacterial species are exposed to various concentrations of the same drug and incubated to determine minimum drug concentration by observing bacterial growth post incubation

Question 7

explain the minimum bactericidal/fungicidal concentration of antimicrobial drugs

Answer 7

the lowest concentration of a drug required to kill a microorganism

Question 8

identify the three phenotypic methods of antimicrobial susceptibility testing

Answer 8

Disk diffusion
Gradient diffusion
Broth microdilution

Question 9

Explain disk diffusion

Answer 9

Using a drug disk and an inoculated agar plate, bacterial susceptibility or resistance can be visualised by a clear ring or lack of surrounding the drug disk post incubation

• can determine MIC

Question 10

explain gradient diffusion

Answer 10

Drug strip with various concentrations is placed on agar plate. Zone of inhibition is larger in higher concentration areas of the stick and decreases as the concentration decreases
- indicates MIC

Question 11

outline the use of antibacterial drugs in the context of treating and
preventing infection

Answer 11

antibacterial drugs
* spectrum of action
o broad spectrum drugs affect both harmful and beneficial species in the GI tract
▪ reduce competition between species / increase levels of resistance genes / reduce diversity
* preoperative prophylaxis - ↓ risks of surgical site infection
* toxicity

Question 12

outline the use of antifungal drugs in the context of treating and
preventing infection

Answer 12

antifungal drugs
* spectrum of action
* route of administration, e.g., oral / topical / intravenous
* toxicity

Question 13

outline the use of anti-HIV drugs in the context of treating and
preventing infection

Answer 13

• combination therapy - single-pill, fixed-dose (e.g., Stribild)
• potential drug-drug interactions
• HIV prevention - PrEP (pre-exposure prophylaxis) / PEP (post-exposure prophylaxis)