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

$$TI = \frac{\text{toxic dose}}{\text{MIC}}$$

Question 1

Which of the following best describes the mechanism of action of β-lactam antibiotics?

Accepted Answer

They block synthesis of peptidoglycan by inhibiting penicillin-binding proteins (PBPs).

Question 2

A patient is prescribed vancomycin for a bacterial infection. Which property makes vancomycin different from β-lactam antibiotics?

Accepted Answer

It inhibits peptide cross-linking in cell wall synthesis, not PBPs.

Question 3

Which of the following drugs is most likely to cause nephrotoxicity and is used primarily against Gram-negative bacteria by disrupting the cell membrane?

Accepted Answer

Polymyxins

Question 4

Aminoglycosides are bactericidal because they:

Accepted Answer

Irreversibly bind to the 30S ribosomal subunit causing misreading of mRNA.

Question 5

Which of the following is a narrow-spectrum drug that interferes with mycolic acid synthesis and is used to treat acid-fast bacteria?

Accepted Answer

Isoniazid

Question 6

Sulfonamides and trimethoprim act as antimetabolites by:

Accepted Answer

Inhibiting enzymes in the folic acid synthesis pathway.

Question 7

Which of the following best explains why β-lactam antibiotics are less effective against Gram-negative bacteria?

Accepted Answer

They cannot penetrate the outer membrane of Gram-negative bacteria.

Question 8

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

Accepted Answer

The microorganism is susceptible to the drug.

Question 9

The minimum inhibitory concentration (MIC) is defined as:

Accepted Answer

The smallest concentration of drug that visibly inhibits microbial growth.

Question 10

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

Accepted Answer

$$TI = \frac{	ext{toxic dose}}{	ext{MIC}}$$

Question 11

Which of the following mechanisms is NOT a common cause of antimicrobial resistance?

Accepted Answer

Inhibition of viral entry into host cells.

Question 12

Fluoroquinolones, such as ciprofloxacin, inhibit bacterial growth by:

Accepted Answer

Binding to topoisomerases or gyrases, interfering with DNA supercoiling and separation.

Question 13

Which of the following statements about antiviral agents is TRUE?

Accepted Answer

They are usually highly selective for viral targets and not broad spectrum.

Question 14

Nucleoside/nucleotide analogs are used as antiviral drugs because they:

Accepted Answer

Mimic natural nucleotides, interfering with viral DNA/RNA polymerases.

Question 15

Which of the following is a major concern with the overuse of fluoroquinolones?

Accepted Answer

Development of resistant bacteria.

Question 16

A patient with HIV is treated with a combination of drugs including AZT, a protease inhibitor, and an integrase inhibitor. What is the rationale for combination therapy?

Accepted Answer

To target multiple viral processes and reduce the likelihood of resistance.

Question 17

Which of the following drugs blocks the activity of viral neuraminidase, preventing release of influenza virus from cells?

Accepted Answer

Oseltamivir (Tamiflu)

Question 18

Which of the following is a real-world example of synergistic drug action?

Accepted Answer

Sulfonamides and trimethoprim used together to inhibit folic acid synthesis.

Question 19

Which of the following statements about Type I interferons is FALSE?

Accepted Answer

They directly inhibit bacterial cell wall synthesis.

Control of Microorganisms: Antimicrobial Drugs and Resistance

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