Q: Which equation correctly represents the therapeutic index (TI) of a drug?

$$TI = \frac{\text{Toxic Dose}}{\text{Therapeutic Dose}}$$

Question 1

Which of the following best defines an antimicrobial drug?

Accepted Answer

A compound that selectively kills or inhibits the growth of microbes with minimal harm to the host.

Question 2

Alexander Fleming discovered penicillin after observing a 'zone of inhibition' on a plate contaminated with mold. What genus of fungus produces penicillin?

Accepted Answer

Penicillium

Question 3

Why might a physician initially prescribe a broad-spectrum antibiotic as empiric therapy?

Accepted Answer

Because the specific pathogen is not yet identified, and broad-spectrum drugs cover a wide range of possible microbes.

Question 4

Which of the following is a potential risk of using broad-spectrum antibiotics?

Accepted Answer

Development of a superinfection due to disruption of normal microbiota.

Question 5

What is the main advantage of semisynthetic antimicrobials over natural antibiotics?

Accepted Answer

They can be chemically modified to improve spectrum, stability, and reduce toxicity.

Question 6

Which equation correctly represents the therapeutic index (TI) of a drug?

Accepted Answer

$$TI = \frac{	ext{Toxic Dose}}{	ext{Therapeutic Dose}}$$

Question 7

A drug with a narrow therapeutic index is more likely to:

Accepted Answer

Cause toxic effects at doses close to the effective dose.

Question 8

Which of the following is a reason why developing antiviral drugs is more challenging than developing antibacterial drugs?

Accepted Answer

Viruses use host cell machinery for replication, making it difficult to target the virus without harming host cells.

Question 9

Which of the following best describes selective toxicity?

Accepted Answer

The ability of a drug to target microbial processes without harming the host.

Question 10

Which organ is most commonly affected by nephrotoxic antimicrobial drugs?

Accepted Answer

Kidneys

Question 11

Which of the following is a correct statement about bacteriostatic drugs?

Accepted Answer

They inhibit bacterial growth, relying on the host immune system to clear the infection.

Question 12

Which of the following is NOT a common target of antibacterial drugs?

Accepted Answer

Mitochondrial DNA synthesis

Question 13

Which of the following best explains why antifungal drugs often have higher toxicity than antibacterial drugs?

Accepted Answer

Fungi are eukaryotic like human cells, so there are fewer unique targets.

Question 14

Which of the following is a mechanism by which bacteria can acquire resistance to antimicrobial drugs?

Accepted Answer

Horizontal gene transfer via plasmids

Question 15

A patient is prescribed an antibiotic with a half-life of 2 hours. What does this mean?

Accepted Answer

Half of the drug will be eliminated from the body every 2 hours.

Question 16

Which of the following best describes the Kirby-Bauer disk diffusion test?

Accepted Answer

It measures the zone of inhibition around antibiotic disks to determine susceptibility.

Question 17

What is the main difference between the MIC and MBC of an antibiotic?

Accepted Answer

MIC is the lowest concentration that inhibits growth; MBC is the lowest concentration that kills 99.9% of bacteria.

Question 18

Which of the following is an example of intrinsic resistance?

Accepted Answer

Mycoplasma pneumoniae is resistant to penicillin because it lacks a cell wall.

Question 19

Which of the following is a key principle of antimicrobial stewardship?

Accepted Answer

Using narrow-spectrum drugs whenever possible and following up with culture results.

Question 20

Which of the following is NOT a recommended action for patients to help reduce antimicrobial resistance?

Accepted Answer

Demanding antibiotics for viral infections.

Antimicrobial Drugs: Principles, Mechanisms, and Resistance

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