Question 1

Which of the following best explains why beta-lactam antibiotics, such as penicillin, are selectively toxic to bacteria but not to human cells?

Accepted Answer

They inhibit the synthesis of peptidoglycan, which is unique to bacterial cell walls.

Question 2

A patient is prescribed an antibiotic that targets the 70S ribosome. Which of the following is a potential side effect due to the similarity between prokaryotic and eukaryotic ribosomes?

Accepted Answer

Damage to mitochondrial function in human cells

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 in fungal membranes

Question 4

A Kirby-Bauer disk diffusion test is performed. What does a large zone of inhibition around an antibiotic disk indicate?

Accepted Answer

The microorganism is sensitive to the antibiotic.

Question 5

Which of the following best describes the mechanism of action of sulfonamides?

Accepted Answer

They act as competitive inhibitors of the enzyme that converts PABA to dihydrofolic acid.

Question 6

Why are broad-spectrum antibiotics more likely to cause superinfections?

Accepted Answer

They kill normal flora, reducing microbial antagonism and allowing opportunistic pathogens to thrive.

Question 7

Which of the following is NOT a common mechanism by which bacteria develop resistance to antibiotics?

Accepted Answer

Increased uptake of the antibiotic into the cell

Question 8

A patient is prescribed tetracycline. Which of the following side effects is most likely to occur if the patient is a child?

Accepted Answer

Permanent discoloration of teeth due to calcium complex formation

Question 9

Which of the following statements about the administration of antimicrobial drugs is correct?

Accepted Answer

Intravenous administration achieves the highest drug concentration in the shortest time.

Question 10

Which of the following best explains why there are fewer effective antiviral drugs compared to antibacterial drugs?

Accepted Answer

Viruses use host cell machinery for replication, making selective toxicity difficult.

Question 11

Which of the following is the correct equation for calculating the therapeutic index (TI) of an antimicrobial drug?

Accepted Answer

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

Question 12

Which of the following best describes the action of Tamiflu (oseltamivir) in treating influenza?

Accepted Answer

It inhibits neuraminidase, preventing the release of new virions from infected cells.

Question 13

A bacterial population is exposed to an antibiotic. Over time, most cells become resistant. Which process best explains this phenomenon?

Accepted Answer

Natural selection, where resistant mutants survive and reproduce.

Question 14

Which of the following is a reason why semisynthetic derivatives of beta-lactams are clinically useful?

Accepted Answer

They are more stable in acidic environments and less susceptible to deactivation.

Question 15

Which of the following best describes the mechanism of action of aminoglycosides such as streptomycin?

Accepted Answer

They cause misreading of mRNA by changing the shape of the 30S ribosomal subunit.

Question 16

Which of the following is a potential consequence of not completing a prescribed course of antibiotics?

Accepted Answer

Surviving bacteria may be resistant and multiply, leading to a resistant population.

Question 17

Which of the following is the primary reason why antimicrobial agents are produced by fungi and bacteria in nature?

Accepted Answer

To inhibit the growth of competing microorganisms in their environment.

Question 18

Which of the following is the best strategy to retard the development of antibiotic resistance in bacterial populations?

Accepted Answer

Use high concentrations of the drug for an appropriate duration and limit use to necessary cases.

Question 19

Which of the following best describes the action of nucleic acid analogs such as acyclovir?

Accepted Answer

They are incorporated into viral DNA, causing premature chain termination.

Controlling Microbial Growth in the Body: Antimicrobial Drugs and Resistance

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