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Ch. 22 - Pathogenic Fungi
Bauman - Microbiology with Diseases by Taxonomy 6th Edition
Bauman6th EditionMicrobiology with Diseases by TaxonomyISBN: 9780134832302Not the one you use?Change textbook
Chapter 22, Problem 1

Amphotericin B is considered the “gold standard” of antifungal agents. Technically, its mode of action works against most fungal infections. Why, then, isn’t it prescribed for most fungal infections?

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Step 1: Understand the mode of action of Amphotericin B. It binds to ergosterol, a key component of fungal cell membranes, creating pores that increase membrane permeability and cause cell death.
Step 2: Recognize that while Amphotericin B is effective against a broad range of fungi, its interaction with ergosterol can also affect cholesterol in human cell membranes, leading to toxicity.
Step 3: Identify the main side effects associated with Amphotericin B, such as nephrotoxicity (kidney damage), infusion-related reactions, and electrolyte imbalances, which limit its use.
Step 4: Consider that due to these toxic effects, Amphotericin B is often reserved for severe or life-threatening fungal infections where benefits outweigh risks.
Step 5: Note that for less severe fungal infections, safer antifungal agents with fewer side effects are preferred, which explains why Amphotericin B is not prescribed for most fungal infections despite its effectiveness.

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Key Concepts

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

Mode of Action of Amphotericin B

Amphotericin B binds to ergosterol, a key component of fungal cell membranes, creating pores that cause ion leakage and cell death. This mechanism makes it effective against a broad range of fungi by disrupting membrane integrity.
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Toxicity and Side Effects

Despite its effectiveness, Amphotericin B has significant toxicity, especially nephrotoxicity (kidney damage), infusion-related reactions, and electrolyte imbalances. These adverse effects limit its use to severe or resistant fungal infections.
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Alternative Antifungal Agents

Other antifungal drugs, such as azoles and echinocandins, have fewer side effects and are easier to administer. These alternatives are preferred for less severe infections, reserving Amphotericin B for cases where other treatments fail or are inappropriate.
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