Question 1

Which of the following best describes the principle of selective toxicity in antimicrobial therapy?

Accepted Answer

The drug targets structures or pathways unique to the pathogen, minimizing harm to the host.

Question 2

A patient is prescribed a beta-lactam antibiotic for a bacterial infection. Which of the following best explains how this drug works?

Accepted Answer

It binds to enzymes responsible for cross-linking NAM subunits, weakening the cell wall.

Question 3

Which of the following drugs would be most effective against a fungal infection and why?

Accepted Answer

Amphotericin B, because it binds to ergosterol and creates pores in fungal membranes.

Question 4

A bacterial strain is found to be resistant to both penicillin and cephalosporin due to a single mechanism. This is an example of:

Accepted Answer

Cross resistance

Question 5

Which of the following best explains why sulfanilamide is selectively toxic to bacteria but not to humans?

Accepted Answer

It blocks folic acid synthesis, a pathway present in bacteria but not in humans who obtain folic acid from their diet.

Question 6

A patient develops a secondary infection after taking a broad-spectrum antibiotic. What is the most likely explanation for this occurrence?

Accepted Answer

The antibiotic disrupted the normal microbiota, reducing microbial antagonism and allowing opportunistic pathogens to grow.

Question 7

Which of the following is NOT a mechanism by which bacteria can become resistant to antimicrobial drugs?

Accepted Answer

Increased uptake of the drug into the cell

Question 8

A new antiviral drug prevents the uncoating of viral capsids after entry into host cells. What is the likely effect of this drug?

Accepted Answer

It prevents the viral genome from being released, thereby blocking viral replication.

Question 9

Which of the following best describes the therapeutic index (TI) of a drug?

Accepted Answer

The ratio of the dose toxic to 50% of the population to the dose therapeutic in 50% of the population: $$TI = \frac{	ext{Toxic Dose}}{	ext{Therapeutic Dose}}$$

Question 10

Which of the following is a major disadvantage of intravenous (IV) administration of antimicrobial drugs?

Accepted Answer

It requires trained personnel and carries a higher risk of introducing infection.

Question 11

A patient is treated with a combination of two antibiotics that work better together than alone. This effect is known as:

Accepted Answer

Synergism

Question 12

Which of the following is a characteristic of an ideal antimicrobial drug?

Accepted Answer

It is nontoxic, nonallergenic, and selectively toxic against a wide range of pathogens.

Question 13

Which of the following best explains why protein synthesis inhibitors can sometimes cause side effects in humans?

Accepted Answer

They target 70S ribosomes, which are also present in human mitochondria.

Question 14

Which of the following is the correct sequence of events in the development of a resistant microbial population after exposure to an antimicrobial drug?

Accepted Answer

Sensitive cells are killed, resistant cells survive and reproduce, leading to a resistant population.

Question 15

Which of the following is NOT a recommended strategy to retard the development of antimicrobial resistance?

Accepted Answer

Stopping treatment as soon as symptoms improve.

Question 16

A bacterium acquires an R plasmid through conjugation. What is the most likely consequence?

Accepted Answer

The bacterium gains resistance to one or more antimicrobial drugs.

Question 17

Which of the following mechanisms allows bacteria in biofilms to resist antimicrobial drugs more effectively than free-living cells?

Accepted Answer

The biofilm matrix slows drug penetration and protects cells from environmental stress.

Question 18

Which of the following best distinguishes narrow-spectrum from broad-spectrum antimicrobial drugs?

Accepted Answer

Broad-spectrum drugs are effective against many types of organisms but may disrupt normal microbiota.

Question 19

Which of the following is a possible result of a low therapeutic index for an antimicrobial drug?

Accepted Answer

Small dosing errors may lead to toxic side effects.

Question 20

Which of the following is a correct example of horizontal gene transfer leading to antimicrobial resistance?

Accepted Answer

A bacterium acquires a resistance gene from another cell via conjugation.

Chapter 10: Controlling Microbial Growth in the Body – Antimicrobial Drugs

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