Question 1

Which of the following best describes the mechanism of action of the antibiotic polymyxin?

Accepted Answer

It disrupts the cytoplasmic membrane by binding to phospholipids, causing leakage of cellular contents.

Question 2

Why are azole antifungal drugs generally less toxic to humans than to fungi?

Accepted Answer

Azoles target ergosterol, which is not synthesized by human cells.

Question 3

A patient is diagnosed with a Mycobacterium tuberculosis infection that is resistant to most antibiotics. Which drug is most likely to be effective due to its unique ability to disrupt the cytoplasmic membrane of this pathogen?

Accepted Answer

Pyrazinamide

Question 4

Which of the following drugs acts by binding to ergosterol in fungal membranes, forming a channel that disrupts membrane integrity?

Accepted Answer

Amphotericin B

Question 5

Which of the following statements about allylamines is correct?

Accepted Answer

They inhibit the synthesis of ergosterol in fungal membranes.

Question 6

A new antifungal drug is found to inhibit the synthesis of ergosterol. Which class of drugs does it most likely belong to?

Accepted Answer

Azoles

Question 7

Which of the following is a reason why polymyxin is typically reserved for use against external pathogens and not for internal use?

Accepted Answer

It is highly toxic to human kidneys.

Question 8

Which of the following equations best represents the effect of amphotericin B on fungal cell membrane permeability?

Accepted Answer

$$\Delta P = P_{after} - P_{before}$$, where $$\Delta P is $$the change in permeability$

Question 9

A patient with a parasitic worm infection is treated with a drug that changes the permeability of the worm's cell membranes. Which drug is most likely being used?

Accepted Answer

Ivermectin

Question 10

Which of the following best explains why amphotericin B is more effective against fungi than against human cells?

Accepted Answer

Fungal membranes contain ergosterol, which is the target of amphotericin B, while human membranes contain cholesterol.

Question 11

Which of the following is NOT a mechanism by which drugs disrupt cytoplasmic membranes?

Accepted Answer

Inhibiting peptidoglycan cross-linking

Question 12

A fungal infection is being treated with a drug that inhibits the enzyme responsible for converting lanosterol to ergosterol. Which class of drugs is being used?

Accepted Answer

Azoles

Question 13

Which of the following drugs is most likely to cause nephrotoxicity as a side effect when used systemically?

Accepted Answer

Polymyxin

Question 14

Which of the following best describes the selectivity of azole antifungals?

Accepted Answer

They inhibit ergosterol synthesis, which is unique to fungi.

Question 15

A patient is prescribed terbinafine for a fungal infection. What is the primary mechanism of action of this drug?

Accepted Answer

Inhibition of ergosterol synthesis by blocking squalene epoxidase.

Question 16

Which of the following drugs would be most appropriate for treating a Gram-negative bacterial infection that is resistant to most other antibiotics, but should be used with caution due to toxicity?

Accepted Answer

Polymyxin

Question 17

Which of the following best explains why pyrazinamide is effective against Mycobacterium tuberculosis?

Accepted Answer

It disrupts the cytoplasmic membrane and accumulates inside the bacterium.

Question 18

Which of the following is a common feature of drugs that disrupt cytoplasmic membranes?

Accepted Answer

They often cause leakage of cellular contents, leading to cell death.

Question 19

Which of the following equations best represents the relationship between drug concentration ($$C) $$and membrane disruption effect ($$E) $$for a drug that follows a sigmoidal dose-response curve?

Accepted Answer

$$E = \frac{E_{max} \cdot C^n}{EC_{50}^n + C^n}$$

Disruption of Cytoplasmic Membranes: Antimicrobial Drugs and Mechanisms

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