Ch. 15 - Antimicrobial Drugs

Norman-McKay- Microbiology: Basic and Clinical Principles 2nd Edition

Norman-McKay2nd EditionMicrobiology: Basic and Clinical PrinciplesISBN: 9780137661619Not the one you use?Change textbook

Norman-McKay 2nd Edition

Ch. 15 - Antimicrobial Drugs

Problem 16

Chapter 15, Problem 16

Choose the false statement(s). Select all that apply.
a. Antifungal drugs may target cholesterol in fungal cell membranes.
b. Azole and polyene drugs promote cell lysis by impacting fungal cell plasma membranes.
c. Echinocandin drugs inhibit fungal cell wall synthesis.
d. Antifungal drugs may target DNA replication.
e. Antifungal drugs may target protein synthesis.

Verified step by step guidance

Step 1: Understand the target structures and processes of antifungal drugs. Antifungal drugs typically target components unique to fungi, such as ergosterol in the fungal cell membrane or the fungal cell wall, which contains glucans and chitin.

Step 2: Evaluate statement (a). Cholesterol is a component of animal cell membranes, while fungi have ergosterol instead. Therefore, antifungal drugs target ergosterol, not cholesterol, in fungal membranes. This suggests statement (a) is false.

Step 3: Evaluate statement (b). Azoles inhibit ergosterol synthesis, and polyenes bind to ergosterol, disrupting fungal plasma membranes and causing cell lysis. This is a true statement.

Step 4: Evaluate statement (c). Echinocandins inhibit the synthesis of β-glucan, an essential component of the fungal cell wall, making this statement true.

Step 5: Evaluate statements (d) and (e). Antifungal drugs generally do not target DNA replication or protein synthesis directly, as these processes are similar in fungi and human cells, making selective targeting difficult. Therefore, these statements are false.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Fungal Cell Membrane Composition

Fungal cell membranes contain ergosterol, not cholesterol, which is the primary target of many antifungal drugs. Understanding this difference is crucial because drugs like azoles and polyenes bind to ergosterol to disrupt membrane integrity, leading to fungal cell death.

Mechanism of Action of Antifungal Drug Classes

Azoles inhibit ergosterol synthesis, and polyenes bind ergosterol to create membrane pores, both causing cell membrane disruption. Echinocandins inhibit synthesis of β-glucan, a key component of the fungal cell wall, weakening structural integrity and causing cell lysis.

Targets of Antifungal Drugs Beyond Membranes and Cell Walls

Unlike antibacterial drugs, most antifungals do not target DNA replication or protein synthesis in fungi. These processes are less commonly targeted due to similarities between fungal and human cells, which increases toxicity risk.

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Related Practice

Textbook Question

Mark the following as true or false, and then correct the false statements so they are true.

a. Human cells make drug efflux pumps.

b. The minimum bactericidal concentration is the minimum concentration of the drug that kills at least 50 percent of the bacteria present.

c. The E-test can reveal if a drug is bactericidal or bacteriostatic.

d. A drug that is bactericidal at one dose may be bacteriostatic at another dose.

e. The antifolate combination therapy trimethoprim-sulfamethoxazole may be used to treat protozoan infections.

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Textbook Question

Acquired antibiotic resistance can include all of the following except:

a. Altering an enzyme that a given drug may target

b. Making endospores

c. Altering a point of entry for a drug

d. Making enzymes that inactivate a drug

e. Increasing the number of efflux pumps that are active in a cell

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Textbook Question

Why is it challenging to obtain selectively toxic drugs against fungi, protozoans, and viruses?

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Textbook Question

Which sensitivity test is best for determining the minimum bactericidal concentration and the minimum inhibitory concentration of a drug?

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Textbook Question

Match the antimicrobial drug to its feature. Some features may be used more than once, and some may not be used at all.

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