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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
All textbooksBauman 6th EditionCh. 22 - Pathogenic FungiProblem 11
Chapter 22, Problem 11

A spherule stage is seen in humans infected with what organism?
a. Blastomyces dermatitidis
b. Coccidioides immitis
c. Histoplasma capsulatum
d. Paracoccidioides brasiliensis

Verified step by step guidance
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Step 1: Understand the term 'spherule stage' in the context of fungal infections. A spherule is a large, thick-walled structure containing endospores, characteristic of certain dimorphic fungi during infection in humans.
Step 2: Review the life cycles and morphological forms of the listed fungi when infecting humans: Blastomyces dermatitidis, Coccidioides immitis, Histoplasma capsulatum, and Paracoccidioides brasiliensis.
Step 3: Recall that Blastomyces dermatitidis typically forms broad-based budding yeast in tissue, not spherules.
Step 4: Recognize that Histoplasma capsulatum appears as small intracellular yeasts within macrophages, not spherules.
Step 5: Identify that Coccidioides immitis is known for forming spherules filled with endospores in human tissue, which is a distinctive diagnostic feature.

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Key Concepts

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

Spherule Stage in Fungal Life Cycles

The spherule is a specialized, thick-walled structure formed by certain fungi during infection in humans. It contains endospores and is a key diagnostic feature, especially in tissue samples. Understanding which fungi produce spherules helps identify the causative agent of specific fungal infections.
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Coccidioides immitis and Coccidioidomycosis

Coccidioides immitis is a dimorphic fungus that causes coccidioidomycosis (Valley fever). In the human host, it transforms into spherules filled with endospores, which rupture to release new infectious particles. This spherule stage is unique to Coccidioides among the listed fungi.

Differentiation of Dimorphic Fungi

Dimorphic fungi like Blastomyces, Histoplasma, and Paracoccidioides have distinct morphological forms in the environment and in human tissue. Recognizing their specific tissue forms—such as yeast, intracellular forms, or spherules—is essential for accurate diagnosis and treatment.
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Related Practice
Textbook Question

Which of the following systemic mycoses is endemic to the deserts of the southwestern

United States?

a. Blastomycosis

b. Coccidioidomycosis

c. Histoplasmosis

d. Paracoccidioidomycosis

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Textbook Question

Ergot alkaloids are produced by some strains of the genus _____ .

Textbook Question

The number of mycoses and cases of microsporidiosis worldwide are rising, in part because ______.

a. the number of fungi in the environment is rising

b. the number of immunocompromised individuals in the population is rising

c. fungi have become more pathogenic

d. fungi are developing a new tendency to spread between people

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Textbook Question

Fungal allergens generally stimulate what type of reaction?

a. Type I hypersensitivity

b. Type II hypersensitivity

c. Type III hypersensitivity

d. Type IV hypersensitivity

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Textbook Question

Of the following fungal diseases, which is found in almost all terminal AIDS patients?

a. Chromoblastomycosis

b. Blastomycosis

c. Candidiasis

d. Mycetoma

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Textbook Question

Indicate whether each statement is true or false. If the statement is false, change the underlined word or phrase to make the statement true.


_____ Almost everyone has allergies to fungal elements.

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