Mycology

29 ASCP MLS practice questions on Mycology, part of Microbiology. The first 25 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

Question 1 · Hard
An 8-year-old girl has patchy hair loss with hairs broken off at the scalp, leaving black dots; two classmates have similar lesions. The scalp does not fluoresce under a Wood's lamp. A KOH mount of plucked hairs shows chains of arthroconidia packed inside the hair shaft. After 14 days on Sabouraud agar with cycloheximide, a slow-growing, suede-like colony with a deep mahogany-red reverse appears. Microconidia vary from teardrop shapes to large balloon forms, and macroconidia are rare. Growth is much better on agar with added thiamine. Which dermatophyte is most likely?
1. AMicrosporum canis
2. BTrichophyton tonsurans
3. CMicrosporum audouinii
4. DTrichophyton rubrum
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Answer: B · Trichophyton tonsurans
Black-dot tinea capitis with no Wood's lamp fluorescence and arthroconidia inside the hair shaft (endothrix) points to Trichophyton tonsurans, the leading cause of tinea capitis in the United States, which spreads between children. The culture confirms it: a slow, suede-like colony with a red-brown reverse, microconidia of many shapes including balloon forms, and growth enhanced by thiamine. Microsporum canis and M. audouinii cause ectothrix infection and usually fluoresce, and M. canis forms large spindle-shaped macroconidia. T. rubrum also has a red reverse and teardrop microconidia, but it rarely infects hair and does not need thiamine. Oral therapy is needed, because topical agents do not reach the hair shaft.
- A: M. canis is ectothrix, usually fluoresces and has spindle-shaped macroconidia.
- C: M. audouinii is ectothrix and usually fluoresces under a Wood's lamp.
- D: T. rubrum rarely infects the scalp and does not need thiamine.
Question 2 · Hard
A 55-year-old man who farmed in rural Brazil before moving to the US has had slowly enlarging, warty, cauliflower-like plaques on his lower leg for 10 years. A biopsy shows granulomas containing thick-walled, chestnut-brown, round cells 5-12 µm across that divide by internal cross walls; there are no hyphae, grains or budding yeasts. After 3 weeks, culture grows a slow, velvety olive-black mold. Its conidiophores bear short chains of conidia in more than one pattern, including Rhinocladiella-type and Cladosporium-type sporulation. Which organism is most likely?
1. AMadurella mycetomatis
2. BFonsecaea pedrosoi
3. CExophiala jeanselmei
4. DSporothrix schenckii
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Answer: B · Fonsecaea pedrosoi
Brown, thick-walled cells that divide by cross walls are sclerotic (Medlar) bodies, the tissue form that defines chromoblastomycosis. The warty, slowly spreading leg lesion in a farm worker from the tropics fits that diagnosis. Fonsecaea pedrosoi is its most common agent, and in culture it is a slow, velvety, olive-black mold with mixed sporulation of the Rhinocladiella and Cladosporium types. Exophiala causes phaeohyphomycosis, with brown hyphae in tissue, and Madurella causes eumycetoma, with grains and draining sinuses. Sporothrix forms small cigar-shaped yeasts in tissue and rosettes of conidia in culture.
- A: Madurella causes eumycetoma, with grains and draining sinuses.
- C: Exophiala shows brown hyphae and yeast cells in tissue, not sclerotic bodies.
- D: Sporothrix forms cigar-shaped yeasts in tissue, not sclerotic bodies.
Question 3 · Hard
Three weeks after nearly drowning in a polluted farm pond, a 19-year-old man develops a brain abscess. Tissue shows narrow, septate hyphae branching at acute angles, and the pathologist suggests Aspergillus. In 4 days, the culture grows a fast, white-to-smoky-gray woolly mold with a dark reverse, which also grows on agar containing cycloheximide. The tease mount shows hyaline septate hyphae bearing single, oval, pale-brown conidia with cut-off (truncate) bases on long or short conidiophores. No vesicles, chains of phialides or swollen annellides are seen. The most likely identification is:
1. AFusarium solani complex
2. BAspergillus fumigatus
3. CLomentospora prolificans
4. DScedosporium apiospermum
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Answer: D · Scedosporium apiospermum
Near-drowning in polluted water followed by a brain abscess is the classic setting for the Scedosporium apiospermum complex. In tissue it looks like Aspergillus, but in culture it forms a gray woolly mold that tolerates cycloheximide and bears single oval conidia with truncate bases on simple conidiophores, without the vesicles and phialides of Aspergillus. Lomentospora prolificans has annellides with swollen, flask-shaped bases and a darker colony, and Fusarium forms canoe-shaped macroconidia. Aspergillus fumigatus is inhibited by cycloheximide. The identification matters for treatment: Scedosporium is often resistant to amphotericin B, and voriconazole is the usual first choice.
- A: Fusarium forms canoe-shaped macroconidia.
- B: A. fumigatus forms vesicles with phialides and is inhibited by cycloheximide.
- C: Lomentospora has annellides with swollen bases and a black colony.
Question 4 · Medium
A grey, fluffy mold fills the plate in 3 days. It has broad, sparsely septate hyphae, sporangia, and rhizoids directly below each sporangiophore. Which genus is it?
1. ASyncephalastrum
2. BRhizopus
3. CLichtheimia
4. DMucor
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Answer: B · Rhizopus
Members of the Mucorales grow rapidly and have broad, ribbon-like hyphae with few septa. Rhizopus has rhizoids at the nodes, directly at the base of the sporangiophores. Lichtheimia (formerly Absidia) has rhizoids between the sporangiophores, and Mucor has none. Rhizopus arrhizus is the commonest cause of mucormycosis, such as rhino-orbital-cerebral disease in diabetic ketoacidosis.
- A: Syncephalastrum has tube-like merosporangia around a vesicle.
- C: Lichtheimia has rhizoids between, not below, the sporangiophores.
- D: Mucor has no rhizoids.
Question 5 · Medium
Cryptococcus neoformans forms brown colonies on niger seed (birdseed) agar because it produces:
1. ABeta-galactosidase
2. BUrease
3. CNitrate reductase
4. DPhenol oxidase (laccase)
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Answer: D · Phenol oxidase (laccase)
Niger seed and caffeic acid media contain phenolic compounds that the phenol oxidase (laccase) of Cryptococcus turns into melanin, giving brown to black colonies. Most other yeasts stay cream colored. Both C. neoformans and C. gattii make the pigment, and both are also urease positive and encapsulated. Melanin is a virulence factor that helps the yeast resist oxidative killing.
- A: Beta-galactosidase is not the basis of the niger seed test.
- B: Cryptococcus is urease positive, but urease is detected on urea agar, not by pigment.
- C: Nitrate use is a separate test and does not cause pigment.
Question 6 · Hard
A neutropenic patient with leukemia has painful skin nodules, and the blood cultures grow a mold. The fast-growing, lavender-tinged colony has septate hyphae and canoe-shaped, multicelled macroconidia. The most likely agent is:
1. ARhizopus arrhizus
2. BScedosporium apiospermum
3. CFusarium species
4. DAspergillus fumigatus
Answer and explanation in LearnFree account
Question 7 · Medium
A blue-green, velvety mold grows well at 45 °C. Its phialides form a single row on the upper part of the vesicle only, with conidia in columns. What is the most likely identification?
1. APenicillium species
2. BAspergillus fumigatus
3. CAspergillus flavus
4. DAspergillus niger
Answer and explanation in LearnFree account
Question 8 · Hard
An otherwise healthy man from Vancouver Island has a lung mass and meningitis. An encapsulated, urease-positive yeast grows, and it turns canavanine-glycine-bromothymol blue (CGB) agar blue. What is the most likely identification?
1. ACryptococcus gattii
2. BCryptococcus neoformans
3. CTrichosporon asahii
4. DRhodotorula mucilaginosa
Answer and explanation in LearnFree account
Question 9 · Hard
A sputum culture from a patient who recently moved from Arizona grows a white, cottony mold in 4 days. A tease mount made in the biological safety cabinet shows barrel-shaped arthroconidia alternating with empty cells. The most likely agent is:
1. ABlastomyces dermatitidis
2. BGeotrichum candidum
3. CHistoplasma capsulatum
4. DCoccidioides species
Answer and explanation in LearnFree account
Question 10 · Easy
In tissue, Coccidioides species appear as:
1. ASmall yeasts inside macrophages
2. BYeasts with multiple peripheral buds
3. CLarge yeasts with broad-based buds
4. DSpherules filled with endospores
Answer and explanation in LearnFree account
Question 11 · Easy
Which dermatophyte forms large, rough, thick-walled, spindle-shaped macroconidia with six or more cells?
1. ATrichophyton rubrum
2. BMicrosporum canis
3. CFusarium species
4. DEpidermophyton floccosum
Answer and explanation in LearnFree account
Question 12 · Hard
A yeast from a blood culture of a long-term ventilator patient is identified by an older biochemical panel as Candida haemulonii. The isolate grows at 42 °C and is fluconazole resistant. Which organism should be suspected?
1. ACandida auris
2. BCandida tropicalis
3. CCandida parapsilosis
4. DCandida dubliniensis
Answer and explanation in LearnFree account
Question 13 · Hard
A stem cell transplant recipient on voriconazole prophylaxis develops necrotic sinusitis. Serum galactomannan and 1,3-beta-D-glucan are negative, and tissue shows broad, ribbon-like hyphae with few septa. The most likely agent is:
1. AAspergillus fumigatus
2. BScedosporium apiospermum
3. CFusarium species
4. DRhizopus arrhizus
Answer and explanation in LearnFree account
Question 14 · Easy
Which fungus cannot be grown on routine fungal media and is detected in respiratory specimens by staining or PCR?
1. AHistoplasma capsulatum
2. BPneumocystis jirovecii
3. CAspergillus fumigatus
4. DCryptococcus neoformans
Answer and explanation in LearnFree account
Question 15 · Hard
A mold from a lung transplant recipient's bronchoalveolar lavage forms cinnamon-brown colonies. It has compact columns of conidia on two rows of phialides and single round conidia along the hyphae. To which drug is this species known to be resistant?
1. AVoriconazole
2. BIsavuconazole
3. CAmphotericin B
4. DPosaconazole
Answer and explanation in LearnFree account
Question 16 · Medium
On cornmeal Tween 80 agar, which morphology fits Candida albicans?
1. ABlastoconidia only, with no pseudohyphae
2. BArthroconidia with no blastoconidia
3. CArthroconidia mixed with blastoconidia
4. DPseudohyphae with terminal chlamydoconidia
Answer and explanation in LearnFree account
Question 17 · Hard
A yeast from oral thrush in a patient with HIV is germ tube positive and forms abundant chlamydoconidia, often in pairs and clusters. It fails to grow at 45 °C, while the C. albicans control grows well. What is the most likely identification?
1. ACandida tropicalis
2. BCandida dubliniensis
3. CCandida auris
4. DCandida albicans
Answer and explanation in LearnFree account
Question 18 · Hard
A man with advanced HIV who lives in northern Thailand has fever and umbilicated skin papules. At 25 °C, a mold grows with a red pigment that spreads into the agar; at 37 °C, it forms yeast-like cells that divide by a cross wall. What is the agent?
1. AHistoplasma capsulatum
2. BSporothrix schenckii
3. CCryptococcus neoformans
4. DTalaromyces marneffei
Answer and explanation in LearnFree account
Question 19 · Hard
A neutropenic patient's blood culture grows a dry, wrinkled yeast. It is urease positive, cornmeal agar shows both arthroconidia and blastoconidia, and the serum cryptococcal antigen latex test is weakly positive. The most likely identification is:
1. AGeotrichum candidum
2. BTrichosporon asahii
3. CCandida tropicalis
4. DCryptococcus neoformans
Answer and explanation in LearnFree account
Question 20 · Hard
A patient with AIDS has WBC 1.8 × 10^3/µL (1.8 × 10^9/L), hemoglobin 7.9 g/dL (79 g/L) and platelets 42 × 10^3/µL (42 × 10^9/L). The bone marrow shows macrophages packed with oval organisms 2 to 4 µm long, each with a narrow-based bud and a clear halo, and no kinetoplast. What is the most likely agent?
1. AHistoplasma capsulatum
2. BTalaromyces marneffei
3. CLeishmania donovani
4. DCryptococcus neoformans
Answer and explanation in LearnFree account
Question 21 · Medium
A rose gardener has nodules spreading up the forearm from a thorn wound. At 25 °C, the culture shows thin hyphae with petal-like clusters of conidia at the tips of conidiophores; at 37 °C, cigar-shaped yeasts form. What is the agent?
1. ASporothrix schenckii
2. BBlastomyces dermatitidis
3. CMycobacterium marinum
4. DNocardia brasiliensis
Answer and explanation in LearnFree account
Question 22 · Medium
A slow-growing mold from a lung biopsy has large, thick-walled, knobby (tuberculate) macroconidia. Before Histoplasma capsulatum is reported, it must be confirmed, because similar macroconidia are made by:
1. ASepedonium species
2. BMalbranchea species
3. CChrysosporium species
4. DScopulariopsis species
Answer and explanation in LearnFree account
Question 23 · Medium
A dark, fast-growing mold from a sinus specimen has brown macroconidia with both cross and lengthwise septa, borne in chains and tapering to a beak. The most likely identification is:
1. ABipolaris
2. BAlternaria
3. CCurvularia
4. DCladosporium
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Question 24 · Hard
In a germ tube test, the Candida albicans control shows no germ tubes after 3 hours at 37 °C in fresh pooled human serum. The control suspension was visibly cloudy. The most likely cause is:
1. AIncubation at 37 °C, not 25 °C
2. BAn inoculum that was too heavy
3. CIncubation that was too short
4. DSerum used instead of saline
Answer and explanation in LearnFree account
Question 25 · Medium
A dermatophyte from a foot lesion is either Trichophyton rubrum or Trichophyton mentagrophytes (complex). Which result supports T. mentagrophytes?
1. AGrowth enhanced only by added thiamine
2. BPositive in vitro hair perforation test
3. CNo urease activity after 7 days
4. DWine-red pigment on the colony reverse
Answer and explanation in LearnFree account

4 more Mycology questions

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Mycology

A grey, fluffy mold fills the plate in 3 days. It has broad, sparsely septate hyphae, sporangia, and rhizoids directly below each sporangiophore. Which genus is it?

Cryptococcus neoformans forms brown colonies on niger seed (birdseed) agar because it produces:

A neutropenic patient with leukemia has painful skin nodules, and the blood cultures grow a mold. The fast-growing, lavender-tinged colony has septate hyphae and canoe-shaped, multicelled macroconidia. The most likely agent is:

A blue-green, velvety mold grows well at 45 °C. Its phialides form a single row on the upper part of the vesicle only, with conidia in columns. What is the most likely identification?

An otherwise healthy man from Vancouver Island has a lung mass and meningitis. An encapsulated, urease-positive yeast grows, and it turns canavanine-glycine-bromothymol blue (CGB) agar blue. What is the most likely identification?

A sputum culture from a patient who recently moved from Arizona grows a white, cottony mold in 4 days. A tease mount made in the biological safety cabinet shows barrel-shaped arthroconidia alternating with empty cells. The most likely agent is:

In tissue, Coccidioides species appear as:

Which dermatophyte forms large, rough, thick-walled, spindle-shaped macroconidia with six or more cells?

A yeast from a blood culture of a long-term ventilator patient is identified by an older biochemical panel as Candida haemulonii. The isolate grows at 42 °C and is fluconazole resistant. Which organism should be suspected?

A stem cell transplant recipient on voriconazole prophylaxis develops necrotic sinusitis. Serum galactomannan and 1,3-beta-D-glucan are negative, and tissue shows broad, ribbon-like hyphae with few septa. The most likely agent is:

Which fungus cannot be grown on routine fungal media and is detected in respiratory specimens by staining or PCR?

A mold from a lung transplant recipient's bronchoalveolar lavage forms cinnamon-brown colonies. It has compact columns of conidia on two rows of phialides and single round conidia along the hyphae. To which drug is this species known to be resistant?

On cornmeal Tween 80 agar, which morphology fits Candida albicans?

A yeast from oral thrush in a patient with HIV is germ tube positive and forms abundant chlamydoconidia, often in pairs and clusters. It fails to grow at 45 °C, while the C. albicans control grows well. What is the most likely identification?

A man with advanced HIV who lives in northern Thailand has fever and umbilicated skin papules. At 25 °C, a mold grows with a red pigment that spreads into the agar; at 37 °C, it forms yeast-like cells that divide by a cross wall. What is the agent?

A neutropenic patient's blood culture grows a dry, wrinkled yeast. It is urease positive, cornmeal agar shows both arthroconidia and blastoconidia, and the serum cryptococcal antigen latex test is weakly positive. The most likely identification is:

A rose gardener has nodules spreading up the forearm from a thorn wound. At 25 °C, the culture shows thin hyphae with petal-like clusters of conidia at the tips of conidiophores; at 37 °C, cigar-shaped yeasts form. What is the agent?

A slow-growing mold from a lung biopsy has large, thick-walled, knobby (tuberculate) macroconidia. Before Histoplasma capsulatum is reported, it must be confirmed, because similar macroconidia are made by:

A dark, fast-growing mold from a sinus specimen has brown macroconidia with both cross and lengthwise septa, borne in chains and tapering to a beak. The most likely identification is:

In a germ tube test, the Candida albicans control shows no germ tubes after 3 hours at 37 °C in fresh pooled human serum. The control suspension was visibly cloudy. The most likely cause is:

A dermatophyte from a foot lesion is either Trichophyton rubrum or Trichophyton mentagrophytes (complex). Which result supports T. mentagrophytes?