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

$TI = \frac{\text{Maximum safe dose}}{\text{Minimum effective dose}}$

Question 1

Which of the following best describes why it is more difficult to develop selectively toxic drugs against viruses than against bacteria?

Accepted Answer

Viruses replicate inside host cells and use host cellular machinery.

Question 2

Alexander Fleming discovered penicillin after observing that a mold inhibited the growth of which bacterium?

Accepted Answer

Staphylococcus aureus

Question 3

A patient is prescribed a broad-spectrum antibiotic as empiric therapy. What is a major drawback of this approach?

Accepted Answer

It increases the risk of C. difficile infection due to disruption of normal microbiota.

Question 4

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

Accepted Answer

$TI = \frac{	ext{Maximum safe dose}}{	ext{Minimum effective dose}}$

Question 5

A drug is described as bacteriostatic. In which scenario would this drug be LEAST effective?

Accepted Answer

A patient with a compromised immune system and a severe infection

Question 6

Which of the following is an example of acquired antimicrobial resistance?

Accepted Answer

A bacterium receives a plasmid carrying a beta-lactamase gene via conjugation.

Question 7

Which of the following best explains why sulfa drugs do NOT target human cells?

Accepted Answer

Human cells do not synthesize folic acid and instead obtain it from their diet.

Question 8

A patient is prescribed an antimicrobial drug with a half-life of 8 hours. If the initial dose is 400 mg, how much drug remains in the body after 24 hours, assuming no additional doses are given?

Accepted Answer

$50 	ext{ mg}$

Question 9

Which of the following is a major reason why healthcare settings are considered 'perfect incubators' for antimicrobial resistance?

Accepted Answer

There is a high prevalence of pathogens and frequent use of antimicrobials.

Question 10

Which of the following is NOT a main mechanism by which bacteria can acquire resistance genes?

Accepted Answer

Binary fission

Question 11

A new antimicrobial drug is described as 'third-generation.' What does this indicate about the drug?

Accepted Answer

It has undergone three rounds of chemical modification, likely expanding its spectrum or stability.

Question 12

Which of the following is a potential adverse effect of using a bactericidal drug against a Gram-negative infection?

Accepted Answer

Release of endotoxin due to bacterial cell lysis

Question 13

Which of the following best describes selective toxicity?

Accepted Answer

The drug harms the pathogen without harming host cells.

Question 14

Which of the following is an example of a nephrotoxic effect caused by an antimicrobial drug?

Accepted Answer

Kidney damage after taking aminoglycosides

Question 15

Which of the following is a correct statement about the half-life of a drug?

Accepted Answer

A drug with a long half-life requires less frequent dosing.

Question 16

Which of the following is a reason why antifungal drugs can have side effects related to cholesterol metabolism in humans?

Accepted Answer

Fungal plasma membranes contain ergosterol, which is structurally similar to human cholesterol.

Question 17

Which of the following is NOT a recommended strategy for healthcare workers to reduce the emergence of antimicrobial resistance?

Accepted Answer

Prescribing antibiotics for viral infections to satisfy patient demand

Question 18

Which of the following best explains why drugs that target the 70S ribosome are selectively toxic to bacteria?

Accepted Answer

Bacterial ribosomes are 70S, while human cytoplasmic ribosomes are 80S.

Question 19

Which of the following is an urgent drug-resistant threat according to the CDC?

Accepted Answer

Carbapenem-resistant Enterobacterales (CRE)

Question 20

A patient is prescribed an antimicrobial drug that must be taken every 4 hours for 7 days. What property of the drug most likely explains this dosing schedule?

Accepted Answer

The drug has a short half-life.

Chapter 15: Antimicrobial Drugs – Principles, Mechanisms, and Resistance

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