Nail clippings from a 40-year-old woman show no hyphae in KOH and are cultured on two Sabouraud dextrose agar slants. On day 5, one slant has a single blue-green Penicillium colony away from the inoculum; the other is sterile. How should this be reported?

Probable contaminant; request a repeat

Penicillium onychomycosis; report it

Mixed infection; test antifungal MICs

Dermatophyte; set up a slide culture

Mycology: classification, morphology and identification

36 Kerala PSC Lab Technician Gr II practice questions on Mycology: classification, morphology and identification, 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 · Easy
Broad, aseptate (coenocytic) hyphae are a feature of the class:
1. ABasidiomycetes
2. BDeuteromycetes
3. CAscomycetes
4. DZygomycetes
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Answer: D · Zygomycetes
Zygomycetes, now placed in the order Mucorales, include Rhizopus, Mucor and Lichtheimia. They have broad, ribbon-like hyphae with few or no septa and form asexual sporangiospores inside sporangia. Ascomycetes, basidiomycetes and most deuteromycetes have narrow septate hyphae. In tissue, wide aseptate hyphae with right-angle branching suggest mucormycosis.
- A: Basidiomycetes have septate hyphae, often with clamp connections.
- B: Deuteromycetes (fungi imperfecti) have septate hyphae.
- C: Ascomycetes such as Aspergillus have septate hyphae.
Question 2 · Hard
Nail clippings from a 40-year-old woman show no hyphae in KOH and are cultured on two Sabouraud dextrose agar slants. On day 5, one slant has a single blue-green Penicillium colony away from the inoculum; the other is sterile. How should this be reported?
1. APenicillium onychomycosis; report it
2. BMixed infection; test antifungal MICs
3. CProbable contaminant; request a repeat
4. DDermatophyte; set up a slide culture
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Answer: C · Probable contaminant; request a repeat
Penicillium is one of the commonest airborne laboratory contaminants. A single colony growing away from the inoculated material, on one slant only, from a specimen with a negative KOH mount points to contamination rather than infection. A non-dermatophyte mould is accepted as a nail pathogen only when hyphae are seen in KOH and the same mould grows from several inocula and from repeat samples. A fresh specimen should be requested.
- A: One off-inoculum colony with a negative KOH does not prove nail infection.
- B: Antifungal testing of a contaminant is not useful.
- D: The isolate is a Penicillium, not a dermatophyte.
Question 3 · Medium
A mould from the ear debris of a man with itchy ears forms black, powdery colonies with a pale reverse. Septate hyphae bear round vesicles covered all over with phialides. Which mould is this?
1. AAspergillus niger
2. BRhizopus species
3. CAspergillus fumigatus
4. DPenicillium species
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Answer: A · Aspergillus niger
Aspergillus species have septate hyphae and conidiophores that end in a swollen vesicle bearing phialides, which produce chains of conidia. A. niger has large, round vesicles covered all over with two rows of cells (metulae and phialides) and dark brown-black conidia, giving a black colony with a pale reverse. It is a common cause of otomycosis and a frequent laboratory contaminant. A. fumigatus has blue-green colonies with phialides only on the upper part of the vesicle.
- B: Rhizopus has aseptate hyphae and sporangia, not vesicles with phialides.
- C: A. fumigatus has blue-green colonies and phialides on the upper vesicle only.
- D: Penicillium has brush-like conidiophores with no vesicle.
Question 4 · Medium
Which of these fungi is NOT thermally dimorphic?
1. AAspergillus fumigatus
2. BHistoplasma capsulatum
3. CTalaromyces marneffei
4. DSporothrix schenckii
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Answer: A · Aspergillus fumigatus
Thermally dimorphic fungi grow as moulds at 25-30 °C and as yeasts at 37 °C and in tissue (Coccidioides forms spherules instead). Histoplasma, Sporothrix, Talaromyces (formerly Penicillium) marneffei, Blastomyces and Paracoccidioides behave this way. Aspergillus fumigatus grows as a septate mould at both temperatures and in tissue. Converting a mould to its yeast form at 37 °C helps confirm a dimorphic fungus.
- B: Histoplasma grows as a mould at 25 °C and as small yeasts at 37 °C.
- C: Talaromyces marneffei forms a mould at 25 °C and yeast-like cells dividing by fission at 37 °C.
- D: Sporothrix forms a mould at 25 °C and cigar-shaped yeasts at 37 °C.
Question 5 · Hard
A 24-year-old man has itchy, red groin lesions. Skin scrapings on Sabouraud agar grow a flat, khaki-yellow, suede-like colony in 10 days. Microscopy shows smooth, thin-walled, club-shaped macroconidia in groups of two or three, and no microconidia. Which fungus is this?
1. ATrichophyton mentagrophytes
2. BTrichophyton rubrum
3. CEpidermophyton floccosum
4. DMicrosporum canis
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Answer: C · Epidermophyton floccosum
Dermatophytes are identified by their conidia. Epidermophyton floccosum forms smooth, thin-walled, club-shaped macroconidia singly or in small clusters, and no microconidia; its colonies are khaki to olive-yellow. Trichophyton species produce many microconidia with few pencil-shaped macroconidia, and Microsporum canis has rough, thick-walled, spindle-shaped macroconidia. E. floccosum infects skin and nails but not hair, and is a common cause of tinea cruris.
- A: T. mentagrophytes forms grape-like clusters of round microconidia and spiral hyphae.
- B: T. rubrum forms many teardrop microconidia and often a red reverse.
- D: M. canis has rough, thick-walled, spindle-shaped macroconidia with many cells.
Question 6 · Medium
Branched conidiophores carrying phialides with chains of conidia in a brush-like arrangement, with no vesicle, are typical of:
1. APenicillium
2. BAspergillus
3. CCladosporium
4. DMucor
Answer and explanation in LearnFree account
Question 7 · Easy
Fungi imperfecti (Deuteromycetes) are fungi in which:
1. ANo sexual stage is known
2. BThe hyphae are aseptate
3. CSpores form on a basidium
4. DSpores form inside an ascus
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Question 8 · Medium
A fast-growing, grey, woolly mould has broad, nearly aseptate hyphae and branched sporangiophores carrying round sporangia, with no rhizoids. It is most likely:
1. ALichtheimia (Absidia)
2. BAspergillus
3. CRhizopus
4. DMucor
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Question 9 · Easy
The rigid cell wall of fungi is made mainly of:
1. ACellulose
2. BLipopolysaccharide
3. CChitin and glucans
4. DPeptidoglycan
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Question 10 · Easy
In the morphological classification of fungi, Cryptococcus neoformans is a:
1. AYeast
2. BYeast-like fungus
3. CMould
4. DDimorphic fungus
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Question 11 · Hard
Skin scrapings from a 35-year-old man with tinea corporis grow a white, cottony colony with a deep wine-red reverse. Microscopy shows teardrop microconidia along the hyphae and rare pencil-shaped macroconidia. Urease is negative at 7 days. The fungus is:
1. ATrichophyton mentagrophytes
2. BEpidermophyton floccosum
3. CTrichophyton rubrum
4. DMicrosporum canis
Answer and explanation in LearnFree account
Question 12 · Medium
Pseudohyphae of Candida differ from true hyphae in that they:
1. AHave parallel walls throughout
2. BHave no cross-walls at all
3. CBranch at right angles
4. DAre constricted at each septum
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Question 13 · Easy
At what temperature does a thermally dimorphic fungus grow in its yeast form in culture?
1. A37 °C
2. B25 °C
3. C4 °C
4. D56 °C
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Question 14 · Medium
Cladosporium and Alternaria form olive-black colonies with a black reverse. They are grouped as dematiaceous fungi because:
1. ATheir walls contain melanin
2. BThey grow as yeasts at 37 °C
3. CTheir hyphae have no septa
4. DThey form only sexual spores
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Question 15 · Easy
How do yeasts mainly reproduce asexually?
1. ASporangiospores
2. BBinary fission
3. CHyphal fragmentation
4. DBudding
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Question 16 · Hard
A yeast from the CSF of a 38-year-old man with AIDS gives: germ tube negative, no pseudohyphae on cornmeal agar, urease positive, brown colonies on niger (bird) seed agar, growth at 37 °C. Which yeast is this?
1. ARhodotorula species
2. BCandida albicans
3. CCryptococcus neoformans
4. DCandida tropicalis
Answer and explanation in LearnFree account
Question 17 · Medium
Which of these fungal spores is formed by sexual reproduction?
1. AAscospore
2. BSporangiospore
3. CArthroconidium
4. DChlamydospore
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Question 18 · Easy
Which mould produces sickle- or canoe-shaped macroconidia with several cross-walls?
1. APenicillium
2. BRhizopus
3. CFusarium
4. DAspergillus
Answer and explanation in LearnFree account
Question 19 · Easy
Which dimorphic fungus forms large, thick-walled macroconidia covered with knob-like projections (tuberculate macroconidia) in its mould phase?
1. AHistoplasma capsulatum
2. BSporothrix schenckii
3. CBlastomyces dermatitidis
4. DCoccidioides immitis
Answer and explanation in LearnFree account
Question 20 · Medium
A mould from an HIV-positive man from Manipur produces a red pigment that diffuses into the agar at 25 °C. At 37 °C it forms yeast-like cells that divide by fission. It is:
1. ATalaromyces marneffei
2. BHistoplasma capsulatum
3. CPenicillium chrysogenum
4. DTrichophyton rubrum
Answer and explanation in LearnFree account
Question 21 · Hard
A corneal scraping from a farmer in Madurai grows an olive-black colony with a black reverse. Its brown conidia are curved, with 3 septa and an enlarged, darker central cell. The mould is:
1. ACurvularia
2. BFusarium
3. CAlternaria
4. DCladosporium
Answer and explanation in LearnFree account
Question 22 · Medium
In tissue, a large yeast with a thick, double-contoured wall and a single broad-based bud suggests:
1. ABlastomyces dermatitidis
2. BHistoplasma capsulatum
3. CCryptococcus neoformans
4. DTalaromyces marneffei
Answer and explanation in LearnFree account
Question 23 · Medium
In tissue, which dimorphic fungus forms large, thick-walled spherules filled with endospores?
1. AHistoplasma capsulatum
2. BBlastomyces dermatitidis
3. CCoccidioides immitis
4. DSporothrix schenckii
Answer and explanation in LearnFree account
Question 24 · Easy
Fungi differ from bacteria because fungi are:
1. AUnable to form spores
2. BEukaryotic, with a nuclear membrane
3. CObligate intracellular parasites
4. DProkaryotic, with a peptidoglycan wall
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Question 25 · Medium
In a mould with broad aseptate hyphae, root-like rhizoids lie directly beneath each cluster of sporangiophores. The mould is:
1. AMucor
2. BAspergillus
3. CRhizopus
4. DLichtheimia
Answer and explanation in LearnFree account

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Mycology: classification, morphology and identification

Broad, aseptate (coenocytic) hyphae are a feature of the class:

Nail clippings from a 40-year-old woman show no hyphae in KOH and are cultured on two Sabouraud dextrose agar slants. On day 5, one slant has a single blue-green Penicillium colony away from the inoculum; the other is sterile. How should this be reported?

A mould from the ear debris of a man with itchy ears forms black, powdery colonies with a pale reverse. Septate hyphae bear round vesicles covered all over with phialides. Which mould is this?

Which of these fungi is NOT thermally dimorphic?

A 24-year-old man has itchy, red groin lesions. Skin scrapings on Sabouraud agar grow a flat, khaki-yellow, suede-like colony in 10 days. Microscopy shows smooth, thin-walled, club-shaped macroconidia in groups of two or three, and no microconidia. Which fungus is this?

Branched conidiophores carrying phialides with chains of conidia in a brush-like arrangement, with no vesicle, are typical of:

Fungi imperfecti (Deuteromycetes) are fungi in which:

A fast-growing, grey, woolly mould has broad, nearly aseptate hyphae and branched sporangiophores carrying round sporangia, with no rhizoids. It is most likely:

The rigid cell wall of fungi is made mainly of:

In the morphological classification of fungi, Cryptococcus neoformans is a:

Skin scrapings from a 35-year-old man with tinea corporis grow a white, cottony colony with a deep wine-red reverse. Microscopy shows teardrop microconidia along the hyphae and rare pencil-shaped macroconidia. Urease is negative at 7 days. The fungus is:

Pseudohyphae of Candida differ from true hyphae in that they:

At what temperature does a thermally dimorphic fungus grow in its yeast form in culture?

Cladosporium and Alternaria form olive-black colonies with a black reverse. They are grouped as dematiaceous fungi because:

How do yeasts mainly reproduce asexually?

A yeast from the CSF of a 38-year-old man with AIDS gives: germ tube negative, no pseudohyphae on cornmeal agar, urease positive, brown colonies on niger (bird) seed agar, growth at 37 °C. Which yeast is this?

Which of these fungal spores is formed by sexual reproduction?

Which mould produces sickle- or canoe-shaped macroconidia with several cross-walls?

Which dimorphic fungus forms large, thick-walled macroconidia covered with knob-like projections (tuberculate macroconidia) in its mould phase?

A mould from an HIV-positive man from Manipur produces a red pigment that diffuses into the agar at 25 °C. At 37 °C it forms yeast-like cells that divide by fission. It is:

A corneal scraping from a farmer in Madurai grows an olive-black colony with a black reverse. Its brown conidia are curved, with 3 septa and an enlarged, darker central cell. The mould is:

In tissue, a large yeast with a thick, double-contoured wall and a single broad-based bud suggests:

In tissue, which dimorphic fungus forms large, thick-walled spherules filled with endospores?

Fungi differ from bacteria because fungi are:

In a mould with broad aseptate hyphae, root-like rhizoids lie directly beneath each cluster of sporangiophores. The mould is: