Mycology (Fungi) MCQs With Answers and Explanations

Ten mycology multiple choice questions with answers and explanations, covering the medically important fungi, how they appear in tissue, and the infections they cause. Write down your answers first, then check them against the key and explanations at the end.

Mycology comes from the Greek mukes ("fungus") and -logia ("study"), so it is simply the study of the kingdom Fungi.

1. Which of the following fungi is most likely to be found within reticuloendothelial cells?

a. Histoplasma capsulatum
b. Sporothrix schenckii
c. Cryptococcus neoformans
d. Candida albicans

2. Aspergillosis is recognized in tissue by the presence of:

a. Metachromatic granules
b. Pseudohyphae
c. Septate hyphae
d. Budding cells

3. Fungi often colonize lesions caused by other conditions. Which of the following is least likely to be present as a colonizer?

a. Candida
b. Sporothrix
c. Mucor
d. Aspergillus

4. A girl who pricked her finger while pruning rose bushes develops a local pustule that progresses to an ulcer. Several nodules then develop along the local lymphatic drainage. The most likely agent is:

a. Aspergillus fumigatus
b. Sporothrix schenckii
c. Cryptococcus neoformans
d. Candida albicans

5. Immunocompromised persons suffer from several fungal diseases. Which of the following is the least frequently associated?

a. Cryptococcus neoformans
b. Aspergillus fumigatus
c. Malassezia furfur
d. Mucor species

6. Each of the following statements concerning Cryptococcus neoformans is correct except:

a. Its natural habitat is the soil, especially associated with pigeon feces
b. Budding yeasts are found in the lesions
c. The initial site of infection is usually the lung
d. Pathogenesis is related primarily to the production of exotoxin A

7. Fungal cells that reproduce by budding are seen in the infected tissues of patients with:

a. Candidiasis, cryptococcosis, and sporotrichosis
b. Mycetoma, candidiasis, and mucormycosis
c. Tinea corporis, tinea unguium, and tinea versicolor
d. Sporotrichosis, mycetoma, and aspergillosis

8. Which one of the following is not a characteristic of histoplasmosis?

a. Person-to-person transmission
b. Specific geographic distribution
c. Yeasts in tissue
d. Mycelial phase in the soil

9. Infection with a dermatophyte is most often associated with:

a. Intravenous drug abuse
b. Inhalation of the organism from contaminated bird feces
c. Adherence of the organism to perspiration-moist skin
d. Fecal-oral transmission

10. Each of the following statements concerning Candida albicans is correct except:

a. C. albicans is a budding yeast that forms pseudohyphae when it invades tissue b. C. albicans causes thrush
c. C. albicans is transmitted primarily by respiratory aerosol
d. Impaired cell-mediated immunity is an important predisposing factor to disease

Answer key

1. a. Histoplasma capsulatum
2. c. Septate hyphae
3. b. Sporothrix
4. b. Sporothrix schenckii
5. c. Malassezia furfur
6. d. Pathogenesis is related primarily to the production of exotoxin A
7. a. Candidiasis, cryptococcosis, and sporotrichosis
8. a. Person-to-person transmission
9. c. Adherence of the organism to perspiration-moist skin
10. c. C. albicans is transmitted primarily by respiratory aerosol

Why these are the answers

1. Histoplasma capsulatum. Histoplasma is the classic intracellular fungus: after inhalation, the yeast forms are taken up by macrophages of the reticuloendothelial system (in the lungs, liver, spleen, and bone marrow) and survive and multiply inside them. This is why disseminated histoplasmosis is diagnosed by finding small yeasts packed inside macrophages. The other three are not primarily intracellular in this way.

2. Septate hyphae. In tissue, Aspergillus appears as septate hyphae that branch at acute (roughly 45-degree) angles, a highly recognizable pattern. This is what distinguishes it from the Mucorales (agents of mucormycosis), which show broad, ribbon-like, aseptate hyphae branching at wide angles. Metachromatic granules and budding cells are not features of Aspergillus, and pseudohyphae belong to Candida.

3. Sporothrix. Candida, Mucor, and Aspergillus are all common colonizers, they can be found growing on existing lesions or in the airways without necessarily causing invasive disease. Sporothrix schenckii, by contrast, is a true pathogen introduced by trauma (a thorn prick) and does not simply colonize surfaces, so it is the least likely to be found as a passive colonizer.

4. Sporothrix schenckii. This is the classic story of sporotrichosis, or rose gardener's disease. The fungus is introduced into the skin by a thorn prick, causes a local ulcer, and then spreads up the arm along the lymphatics, producing a chain of nodules (lymphocutaneous spread). The rose-thorn history plus nodules tracking along a lymphatic channel is essentially diagnostic.

5. Malassezia furfur. Cryptococcus, Aspergillus, and Mucor are the archetypal opportunistic invaders of immunocompromised patients (cryptococcal meningitis, invasive aspergillosis, and mucormycosis). Malassezia furfur is mainly a skin commensal that causes tinea (pityriasis) versicolor in healthy people, so it is the least associated with the classic deep mycoses of immunocompromise. Note one exception worth knowing: Malassezia can cause catheter-related bloodstream infection (fungemia), classically in neonates and other patients receiving intravenous lipid emulsion, so it is not entirely harmless in this group, just far less commonly invasive than the other three.

6. Pathogenesis is related primarily to the production of exotoxin A. This is false, so it is the answer. Cryptococcus neoformans has no important exotoxin; its key virulence factor is its thick polysaccharide capsule, which resists phagocytosis (exotoxin A is a Pseudomonas aeruginosa product). The true statements are correct: it lives in soil enriched with pigeon droppings, appears as budding yeasts in lesions, and is acquired by inhalation, so the lung is the initial site before it spreads to the meninges.

7. Candidiasis, cryptococcosis, and sporotrichosis. The question asks which infections show budding (yeast) forms in tissue. Candida (budding yeast with pseudohyphae), Cryptococcus (budding encapsulated yeast), and Sporothrix (cigar-shaped budding yeast in tissue) all do. The other options include molds and dermatophytes that appear as hyphae, not budding yeasts: mycetoma and aspergillosis show filaments, mucormycosis shows aseptate hyphae, and the tineas show dermatophyte hyphae.

8. Person-to-person transmission. This is the exception, since histoplasmosis is not spread person to person. It is acquired from the environment by inhaling spores from soil enriched with bird or bat droppings, which is why it has a specific geographic distribution (for example, river valleys in parts of the Americas). The true characteristics are its geographic clustering, yeasts in tissue, and a mycelial (mold) phase in the soil, reflecting that Histoplasma is a dimorphic fungus (mold in the environment, yeast in the body).

9. Adherence of the organism to perspiration-moist skin. Dermatophytes are the fungi that cause ringworm (the tineas): they live on keratin in the skin, hair, and nails, and infection is favored by warm, moist conditions, sweaty skin, occlusive footwear, and shared damp surfaces. The other routes describe entirely different organisms and are not how ringworm is acquired.

10. C. albicans is transmitted primarily by respiratory aerosol. This is false, so it is the answer. Candida albicans is part of the normal flora of the mouth, gut, and vagina, and disease usually arises from that endogenous flora overgrowing, not from breathing it in. The true statements are correct: it is a budding yeast that forms pseudohyphae when it invades tissue, it causes oral thrush, and impaired cell-mediated immunity (as in HIV or diabetes) predisposes to candidiasis.