What does scalp hair infected with Microsporum canis typically show under a Wood's lamp?

Bright yellow-green fluorescence

A yeast from a urine culture is put in serum at 37 °C. After 2 hours, short filaments are seen, each clearly constricted where it joins the mother cell. This should be read as:

Germ tube negative, as in Candida tropicalis

Germ tube positive, as in Candida dubliniensis

Germ tube positive, as in Candida albicans

An invalid test, to be repeated at 25 °C

In a patient with AIDS and headache, why is the cryptococcal antigen test on CSF preferred to an India ink preparation?

It detects capsular polysaccharide and is far more sensitive

It detects antibody to the capsule and is more specific

It becomes negative as soon as treatment starts

It distinguishes Cryptococcus neoformans from C. gattii

Mycology

39 Kerala MSc MLT Entrance 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
A fast-growing, grey, woolly mould from a sinus biopsy has broad, sparsely septate hyphae. Its rhizoids arise between the sporangiophores rather than beneath them, and its pear-shaped sporangia sit on a funnel-shaped apophysis. The most likely genus is:
1. ACunninghamella
2. BLichtheimia (Absidia)
3. CMucor
4. DRhizopus
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Answer: B · Lichtheimia (Absidia)
All four genera are Mucorales with broad, pauciseptate hyphae, so the position of the rhizoids and the shape of the sporangium decide the genus. Lichtheimia (formerly Absidia) has internodal rhizoids, between the sporangiophores, and pyriform sporangia with a conical apophysis. Rhizopus has rhizoids directly beneath the sporangiophores (nodal) and round sporangia, Mucor has no rhizoids, and Cunninghamella bears single-spored sporangiola on swollen vesicles instead of true sporangia. All can cause rhino-orbital mucormycosis in poorly controlled diabetes.
- A: Cunninghamella forms one-spored sporangiola on swollen vesicles, not pear-shaped sporangia.
- C: Mucor has no rhizoids at all.
- D: Rhizopus has rhizoids directly below the sporangiophores and round sporangia without a prominent apophysis.
Question 2 · Easy
What does scalp hair infected with Microsporum canis typically show under a Wood's lamp?
1. ADull blue-white fluorescence
2. BBright yellow-green fluorescence
3. CCoral-red fluorescence
4. DNo fluorescence at all
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Answer: B · Bright yellow-green fluorescence
Ectothrix infection by Microsporum canis and M. audouinii produces a pteridine pigment that fluoresces bright yellow-green under long-wave UV light. The lamp helps select infected hairs for KOH and culture and to screen contacts. Endothrix infections such as Trichophyton tonsurans and T. violaceum do not fluoresce, so a negative Wood's lamp does not exclude tinea capitis. Coral-red fluorescence is seen in erythrasma, a bacterial infection.
- A: A dull blue-white glow is seen on normal skin and scale, not in infected hair.
- C: Coral-red fluorescence marks erythrasma caused by Corynebacterium minutissimum.
- D: Absent fluorescence is typical of endothrix infection such as Trichophyton tonsurans.
Question 3 · Medium
A yeast from a urine culture is put in serum at 37 °C. After 2 hours, short filaments are seen, each clearly constricted where it joins the mother cell. This should be read as:
1. AGerm tube positive, as in Candida dubliniensis
2. BGerm tube positive, as in Candida albicans
3. CGerm tube negative, as in Candida tropicalis
4. DAn invalid test, to be repeated at 25 °C
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Answer: C · Germ tube negative, as in Candida tropicalis
A true germ tube is a slender outgrowth with parallel walls and no constriction at its point of origin, formed within 2 to 3 hours in serum at 37 °C. A filament that narrows where it leaves the parent cell is a pseudohypha (a pseudo-germ tube), produced by species such as Candida tropicalis. Reading it as positive would wrongly report C. albicans. Tubes should also be read by 3 hours, because longer incubation lets other species form pseudohyphae.
- A: C. dubliniensis also forms true germ tubes without a constriction.
- B: C. albicans forms true germ tubes without a constriction at the base.
- D: The germ tube test is done at 37 °C; 25 °C would not help.
Question 4 · Easy
In Mucor and Rhizopus, the asexual spores formed inside a sac at the tip of a sporangiophore are called:
1. ASporangiospores
2. BConidia
3. CArthroconidia
4. DChlamydospores
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Answer: A · Sporangiospores
The Mucorales produce asexual spores endogenously, inside a sporangium borne on a sporangiophore, and release them when the sporangial wall breaks. Conidia, by contrast, are formed exogenously on conidiophores or phialides, as in Aspergillus and Penicillium. Arthroconidia arise by fragmentation of hyphae, and chlamydospores are thick-walled resting cells. The type of spore is a basis of the morphological classification of fungi.
- B: Conidia are formed outside any sac, on conidiophores or phialides.
- C: Arthroconidia form when hyphae break up at the septa.
- D: Chlamydospores are thick-walled resting cells within or at the end of hyphae.
Question 5 · Medium
In a patient with AIDS and headache, why is the cryptococcal antigen test on CSF preferred to an India ink preparation?
1. AIt detects antibody to the capsule and is more specific
2. BIt becomes negative as soon as treatment starts
3. CIt distinguishes Cryptococcus neoformans from C. gattii
4. DIt detects capsular polysaccharide and is far more sensitive
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Answer: D · It detects capsular polysaccharide and is far more sensitive
The cryptococcal antigen test, by latex agglutination or lateral flow assay, detects the capsular polysaccharide (glucuronoxylomannan) shed into CSF and serum. It is positive in well over 90% of cases of cryptococcal meningitis, whereas India ink finds the encapsulated yeasts in only about half to four-fifths of cases, and fewer in patients without HIV. Antigen titres fall slowly and can stay positive long after successful treatment, so they are not a test of cure. Culture is still needed to obtain the isolate.
- A: The test detects capsular antigen, not antibody; antibody tests are of little use in cryptococcosis.
- B: Antigen titres fall slowly and can stay positive long after treatment.
- C: The usual antigen tests do not separate C. neoformans from C. gattii; CGB agar does.
Question 6 · Hard
A 40-year-old man with HIV from West Bengal has fever, weight loss and hepatosplenomegaly. Bone marrow shows macrophages packed with oval bodies 2-4 µm long, each with a clear halo and no kinetoplast; they stain with Grocott methenamine silver. The rK39 test is negative. The most likely organism is:
1. ACryptococcus neoformans
2. BLeishmania donovani
3. CHistoplasma capsulatum
4. DToxoplasma gondii
Answer and explanation in LearnFree account
Question 7 · Easy
Hard, dark brown to black nodules firmly attached along scalp hair shafts are typical of:
1. AWhite piedra
2. BBlack piedra
3. CTinea nigra
4. DTinea capitis
Answer and explanation in LearnFree account
Question 8 · Medium
Rhinosporidium seeberi, long described in textbooks of mycology, has never been cultured and is now classified as:
1. AAn aquatic protist of the class Mesomycetozoea
2. BA zygomycete closely related to Mucor
3. CA thermally dimorphic ascomycete fungus
4. DA cyanobacterium of the genus Microcystis
Answer and explanation in LearnFree account
Question 9 · Hard
A paddy farmer from Thanjavur has a corneal ulcer after an injury from a rice leaf. KOH mount of the corneal scraping shows septate hyphae. Culture grows, in 3 days, a granular yellow-green colony. LPCB: rough-walled conidiophores ending in round vesicles covered all over by phialides, some in one row and some in two. The most likely organism is:
1. AFusarium solani
2. BAspergillus flavus
3. CAspergillus niger
4. DAspergillus fumigatus
Answer and explanation in LearnFree account
Question 10 · Hard
A yeast from the blood culture of a neutropenic patient on fluconazole prophylaxis is germ tube negative. It forms dry, pale pink colonies with a fuzzy edge on chromogenic agar, and cornmeal agar shows elongated cells branching like crossed matchsticks. Which antifungal should not be relied on for this isolate?
1. AVoriconazole
2. BAmphotericin B
3. CFluconazole
4. DCaspofungin
Answer and explanation in LearnFree account
Question 11 · Medium
When the mould phase of Sporothrix schenckii is subcultured on brain-heart infusion blood agar at 37 °C, it converts to:
1. ASmall, oval to cigar-shaped budding yeasts
2. BSpherules packed with endospores
3. CYeasts with many buds like a pilot's wheel
4. DLarge yeasts with broad-based buds
Answer and explanation in LearnFree account
Question 12 · Medium
Where are the arthroconidia of the dermatophyte found in endothrix tinea capitis?
1. AInside the hair shaft, with the cuticle intact
2. BAs a sheath on the outer surface of the hair
3. COnly in the scale of the surrounding scalp
4. DAs air spaces and hyphae lying along the hair shaft
Answer and explanation in LearnFree account
Question 13 · Medium
A ventilated ICU patient has fever and a new lung infiltrate. The endotracheal aspirate grows Candida albicans with a few pus cells and no other organisms. The usual interpretation is:
1. ALaboratory contamination of the culture plate
2. BAirway colonisation, as Candida pneumonia is rare
3. CPrimary Candida pneumonia needing antifungals
4. DProof of disseminated candidiasis from the blood
Answer and explanation in LearnFree account
Question 14 · Easy
In tissue sections, the hyphae of Aspergillus fumigatus are typically:
1. APigmented brown, with swollen irregular cells
2. BBroad and ribbon-like, with right-angle branching
3. CShort and curved, mixed with round yeast cells
4. DNarrow and septate, with acute-angle branching
Answer and explanation in LearnFree account
Question 15 · Easy
Cryptococcus neoformans is acquired mainly by inhaling yeast cells from soil contaminated with:
1. APigeon droppings
2. BRodent urine
3. CDecaying rice straw
4. DCattle dung
Answer and explanation in LearnFree account
Question 16 · Easy
Chromoblastomycosis, a warty subcutaneous mycosis of the limbs, is caused most often by:
1. ABasidiobolus ranarum
2. BSporothrix schenckii
3. CMadurella mycetomatis
4. DFonsecaea pedrosoi
Answer and explanation in LearnFree account
Question 17 · Medium
Before a mycetoma is treated, the grains must be shown to be fungal or actinomycete mainly because:
1. AOnly eumycetoma spreads from soft tissue into the underlying bone
2. BOnly actinomycetoma can spread from person to person by contact
3. COnly actinomycetoma ever needs surgical excision of the lesion
4. DActinomycetoma, unlike eumycetoma, responds to antibacterials
Answer and explanation in LearnFree account
Question 18 · Medium
On slide culture, which feature best separates Microsporum from Trichophyton?
1. AMicrosporum forms no microconidia at any stage
2. BTrichophyton forms many rough, spindle-shaped macroconidia
3. CTrichophyton never forms any macroconidia
4. DMicrosporum forms many rough, thick-walled macroconidia
Answer and explanation in LearnFree account
Question 19 · Easy
Aflatoxin, a liver carcinogen found in badly stored groundnuts and grain, is produced mainly by:
1. AFusarium solani
2. BAspergillus flavus
3. CAspergillus fumigatus
4. DPenicillium chrysogenum
Answer and explanation in LearnFree account
Question 20 · Hard
A 34-year-old man with HIV, CD4 count 90/µL and on no prophylaxis, has 3 weeks of dry cough and breathlessness. Oxygen saturation falls to 86% on walking, chest CT shows bilateral ground-glass opacities, and serum LDH is 540 U/L. Sputum Gram stain and AFB smears are negative. Which test best confirms the likely diagnosis?
1. ABAL fluid stained by GMS or immunofluorescence
2. BBlood culture in a fungal culture bottle
3. CSerum cryptococcal antigen latex test
4. DSputum culture on Sabouraud dextrose agar
Answer and explanation in LearnFree account
Question 21 · Easy
A calcofluor white mount shows fungi in clinical specimens because the dye:
1. ABinds chitin and fluoresces under ultraviolet light
2. BDissolves keratin so the hyphae become visible
3. CIs a negative stain that outlines the capsule
4. DStains the fungal cell wall deep blue in daylight
Answer and explanation in LearnFree account
Question 22 · Medium
Many patients in India apply steroid-antifungal combination creams to ringworm. A KOH mount from such a steroid-modified lesion (tinea incognito) usually shows:
1. ANo fungus, because the cream has already cleared it
2. BOnly budding yeast cells, as steroids convert the fungus
3. CAbundant hyphae, as steroids suppress local immunity
4. DHyphae only in plucked hairs, never in the scales
Answer and explanation in LearnFree account
Question 23 · Hard
A 28-year-old woman with AIDS has headache for 2 weeks. A CSF India ink preparation shows numerous budding yeasts with wide clear halos. The cryptococcal antigen latex test on undiluted CSF is negative, and the kit's positive and negative controls react correctly. What should the laboratory do next?
1. ATreat the CSF with pronase and retest undiluted
2. BRetest the CSF after serial dilution
3. CReport the India ink finding as an artefact
4. DReport the antigen test as negative
Answer and explanation in LearnFree account
Question 24 · Hard
A 35-year-old farm labourer has had a painless swelling of the left foot with discharging sinuses for 3 years. The pus contains small, soft, white-yellow grains. A Gram stain of a crushed grain shows thin Gram-positive branching filaments less than 1 µm wide, which are partially acid-fast by the modified Ziehl-Neelsen stain with 1% sulphuric acid. The most likely diagnosis and treatment group are:
1. AActinomycetoma due to Nocardia; antibacterial drugs
2. BActinomycosis due to Actinomyces; penicillin
3. CBotryomycosis due to Staphylococcus aureus; antibiotics
4. DEumycetoma due to Madurella; antifungal drugs
Answer and explanation in LearnFree account
Question 25 · Medium
In a biopsy from a nodule of sporotrichosis, where yeasts are scanty, which finding supports the diagnosis?
1. AAsteroid bodies around the yeast cells
2. BLarge yeasts with broad-based single buds
3. CLarge spherules packed with endospores
4. DCopper-coloured sclerotic (Medlar) bodies
Answer and explanation in LearnFree account

14 more Mycology questions

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Mycology

A fast-growing, grey, woolly mould from a sinus biopsy has broad, sparsely septate hyphae. Its rhizoids arise between the sporangiophores rather than beneath them, and its pear-shaped sporangia sit on a funnel-shaped apophysis. The most likely genus is:

What does scalp hair infected with Microsporum canis typically show under a Wood's lamp?

A yeast from a urine culture is put in serum at 37 °C. After 2 hours, short filaments are seen, each clearly constricted where it joins the mother cell. This should be read as:

In Mucor and Rhizopus, the asexual spores formed inside a sac at the tip of a sporangiophore are called:

In a patient with AIDS and headache, why is the cryptococcal antigen test on CSF preferred to an India ink preparation?

Hard, dark brown to black nodules firmly attached along scalp hair shafts are typical of:

Rhinosporidium seeberi, long described in textbooks of mycology, has never been cultured and is now classified as:

When the mould phase of Sporothrix schenckii is subcultured on brain-heart infusion blood agar at 37 °C, it converts to:

Where are the arthroconidia of the dermatophyte found in endothrix tinea capitis?

A ventilated ICU patient has fever and a new lung infiltrate. The endotracheal aspirate grows Candida albicans with a few pus cells and no other organisms. The usual interpretation is:

In tissue sections, the hyphae of Aspergillus fumigatus are typically:

Cryptococcus neoformans is acquired mainly by inhaling yeast cells from soil contaminated with:

Chromoblastomycosis, a warty subcutaneous mycosis of the limbs, is caused most often by:

Before a mycetoma is treated, the grains must be shown to be fungal or actinomycete mainly because:

On slide culture, which feature best separates Microsporum from Trichophyton?

Aflatoxin, a liver carcinogen found in badly stored groundnuts and grain, is produced mainly by:

A calcofluor white mount shows fungi in clinical specimens because the dye:

Many patients in India apply steroid-antifungal combination creams to ringworm. A KOH mount from such a steroid-modified lesion (tinea incognito) usually shows:

In a biopsy from a nodule of sporotrichosis, where yeasts are scanty, which finding supports the diagnosis?