Mycology — MCQs

Mycology Indian Medical PG Practice Questions and MCQs

Question 461: A man has undergone renal transplant and is taking immunosuppressant drug. On biopsy there was presence of budding cells with pseudohyphae. Identify the organism?

A. Invasive candidiasis (Correct Answer)
B. Pneumocystis
C. Invasive aspergillosis
D. Histoplasmosis

Explanation: ***Invasive candidiasis*** - The presence of **budding cells** and **pseudohyphae** on biopsy is a classic histological finding for *Candida* species. - Individuals who have undergone **renal transplant** and are on **immunosuppressant drugs** are at high risk for opportunistic fungal infections, including invasive candidiasis. *Pneumocystis* - *Pneumocystis jirovecii* typically causes pneumonia and is characterized by cysts or trophic forms in lung tissue, not budding cells and pseudohyphae. - While common in immunocompromised patients, its microscopic morphology is distinctly different from *Candida*. *Invasive aspergillosis* - *Aspergillus* species are characterized by **septate hyphae with acute angle branching** (typically 45-degree angles) on microscopy. - They do not form budding cells or pseudohyphae, which are characteristic of *Candida*. *Histoplasmosis* - *Histoplasma capsulatum* appears as **small, oval-shaped yeast cells** (2-4 µm) often found within macrophages. - It does not form pseudohyphae or large budding cells as described in the question.

Question 462: A 34-year-old woman presents with multiple round, scaly patches on her chest and back. The lesions are hypopigmented and slightly pruritic. KOH preparation of skin scrapings shows short, angular hyphae. Which of the following best describes the causative organism's morphology in culture?

A. Branching, septate hyphae with characteristic 'spaghetti and meatballs' appearance (Correct Answer)
B. Non-septate hyphae with sporangiospores
C. Branching, septate hyphae with tear-drop microconidia
D. Pseudohyphae with blastoconidia

Explanation: ***Branching, septate hyphae with characteristic 'spaghetti and meatballs' appearance*** - The clinical presentation of **hypopigmented, scaly patches** on the trunk, especially with mild pruritus, is highly suggestive of **tinea versicolor**. - A **KOH preparation** showing **short, angular hyphae** is characteristic of *Malassezia furfur*, which when cultured, displays both **mycelial elements (spaghetti)** and **yeast forms (meatballs)**. *Non-septate hyphae with sporangiospores* - This morphology is characteristic of **zygomycetes** (e.g., *Rhizopus*, *Mucor*), which cause diseases like mucormycosis, a much more severe and rapidly progressive infection, not tinea versicolor. - **Zygomycetes** are typically associated with invasive infections in immunocompromised individuals. *Branching, septate hyphae with tear-drop microconidia* - This describes the typical dermatophyte, *Trichophyton rubrum*, which causes conditions like tinea pedis, tinea cruris, and tinea corporis, usually presenting with **erythematous, annular lesions** with active borders, different from tinea versicolor. - While it also has septate hyphae, the distinct microconidia morphology differentiates it from *Malassezia*. *Pseudohyphae with blastoconidia* - This morphology is typical of **Candida species**, which cause conditions like candidiasis (e.g., thrush, diaper rash, vulvovaginitis). - Though *Candida* can cause skin infections, the hypopigmentation and characteristic KOH findings of short, angular hyphae are inconsistent with *Malassezia*.

Question 463: A fungal culture shows 'rising sun' pattern. Which microscopic finding would confirm Microsporum canis?

A. Spiral hyphae
B. Banana-shaped macroconidia (Correct Answer)
C. Racquet hyphae
D. Chlamydospores

Explanation: ***Banana-shaped macroconidia*** - The 'rising sun' colonial pattern on fungal culture is characteristic of *Microsporum canis*, and the key microscopic feature confirming this diagnosis is the presence of **spindle-shaped** or **banana-shaped macroconidia** with rough, thick walls. - These macroconidia typically have 6-15 cells and are observed upon microscopic examination of the fungal culture. *Spiral hyphae* - **Spiral hyphae** are a characteristic microscopic feature seen in *Trichophyton mentagrophytes*, not typically in *Microsporum canis*. - They are coiled or corkscrew-like hyphal structures. *Racquet hyphae* - **Racquet hyphae** are microscopic structures with a swollen, club-shaped end resembling a tennis racquet, often found in various dermatophytes but not specifically diagnostic for *Microsporum canis*. - They are considered a less specific morphological feature. *Chlamydospores* - **Chlamydospores** are thick-walled, asexual spores that are resistant to adverse conditions and are commonly seen in other fungi, such as *Candida albicans* (especially terminal chlamydospores), but not a distinguishing feature for *Microsporum canis*. - They are a survival form of the fungus.

Question 464: A fungal culture shows 'slide culture' with 'match stick' appearance. Which microscopic finding would confirm Sporothrix schenckii?

A. Flower vase arrangement
B. Palisading hyphae
C. Rosette of conidia (Correct Answer)
D. Ship-in-bottle appearance

Explanation: ***Rosette of conidia*** - The distinctive "rosette of conidia" or **"flowerette"** arrangement of conidia around the conidiophores is a classic microscopic feature of *Sporothrix schenckii* in culture. - This morphology, combined with the "matchstick" appearance on slide culture, is highly characteristic for identifying this dimorphic fungus. *Flower vase arrangement* - While *Sporothrix schenckii* can have conidia arranged in a flower-like pattern, the specific term "flower vase arrangement" is not the standard or most precise descriptor for its characteristic morphology. - The more accurate and commonly used term describing the conidia arrangement is **"rosette"** or "flowerette" of conidia. *Palisading hyphae* - **Palisading hyphae** refer to hyphae arranged in a fence-like or parallel alignment, which is not a characteristic microscopic feature of *Sporothrix schenckii*. - This morphology might be seen in other fungal species but does not help in identifying *Sporothrix schenckii*. *Ship-in-bottle appearance* - The "ship-in-bottle" appearance is a microscopic characteristic associated with **Exophiala species**, particularly *Exophiala jeanselmei*. - This morphology involves conidia forming along the sides of hyphae, resembling small cells within a vessel, and is not seen in *Sporothrix schenckii*.

Question 465: A fungal culture shows powdery colonies with radial grooves on Sabouraud's agar. Which microscopic finding would most specifically confirm dermatophyte infection?

A. Microconidia in grape-like clusters
B. Broader angle branching
C. Yeast with pseudohyphae
D. Spiral hyphae (Correct Answer)

Explanation: ***Spiral hyphae*** - **Spiral hyphae** are a specific and characteristic microscopic finding in dermatophytes, particularly *Trichophyton mentagrophytes* - These coiled/spiral structures are diagnostic features that help differentiate dermatophytes from other fungal infections - Along with macroconidia and microconidia arrangement, spiral hyphae are key identifying features in dermatophyte culture *Microconidia in grape-like clusters* - While microconidia are present in dermatophytes, the grape-like cluster arrangement (**en grappe**) is seen in various dermatophyte species but is less specific than spiral hyphae - *Microsporum* species show microconidia in different arrangements, but this finding alone is not as diagnostically specific *Broader angle branching* - **Broader angle branching** (usually >45 degrees, often 90 degrees) with ribbon-like, non-septate hyphae is characteristic of **Mucorales** (e.g., *Rhizopus*, *Mucor*) - These are opportunistic molds causing mucormycosis in immunocompromised patients, not dermatophyte infections - Structurally and clinically distinct from dermatophytes *Yeast with pseudohyphae* - **Yeast with pseudohyphae** is the classic microscopic finding for **Candida species** - *Candida* causes superficial candidiasis, not dermatophyte infections (dermatophytosis/tinea) - Dermatophytes are filamentous fungi, not yeasts

Question 466: A fungal culture shows 'flower vase' arrangement of macroconidia. Which microscopic feature would confirm Fusarium species?

A. Chlamydospores
B. Banana-shaped macroconidia (Correct Answer)
C. Racquet hyphae
D. Ship-in-bottle appearance

Explanation: ***Banana-shaped macroconidia*** - The presence of **canoe- or banana-shaped macroconidia** found in a "flower vase" arrangement (sporodochium) is a definitive microscopic characteristic of *Fusarium species*. - These distinctive macroconidia distinguish *Fusarium* from other filamentous fungi. *Chlamydospores* - **Chlamydospores** are thick-walled, asexual spores that can be found in various fungi, including *Candida albicans* and some *Fusarium* species. - However, they are not the primary or most distinctive feature for confirming *Fusarium* species, especially compared to the morphology of its macroconidia. *Racquet hyphae* - **Racquet hyphae** are hyphae with swollen, club-shaped cells at their ends, resembling a tennis racquet. - These are characteristic of dermatophytes, such as *Trichophyton rubrum*, and are not typically seen as a defining feature of *Fusarium*. *Ship-in-bottle appearance* - The "ship-in-bottle" appearance refers to the characteristic morphology of **arthroconidia** in *Coccidioides immitis*, seen in tissue or culture. - This feature is specific to *Coccidioides* and is not associated with *Fusarium species*.

Question 467: A sputum culture shows colonies with 'corn flakes' appearance and distinctive musty earth odor. Which microscopic finding would confirm Aspergillus fumigatus?

A. Septate hyphae with 45-degree branching (Correct Answer)
B. Broad aseptate hyphae
C. Dematiaceous hyphae
D. Pseudohyphae with blastoconidia

Explanation: ***Septate hyphae with 45-degree branching*** - The distinctive **'corn flakes' appearance** and **musty earth odor** in sputum culture are classic macroscopic findings for *Aspergillus fumigatus*. - Microscopically, *Aspergillus* species are characterized by **septate hyphae** that exhibit a characteristic **45-degree (acute-angle) branching** pattern. *Broad aseptate hyphae* - This morphology is characteristic of **Zygomycetes** (e.g., *Rhizopus*, *Mucor*), which cause mucormycosis. - These fungi typically show **non-septate** or sparsely septate hyphae with **irregular, wide-angle branching**. *Dematiaceous hyphae* - This term refers to **pigmented (dark-walled) hyphae** and is characteristic of various fungi that cause phaeohyphomycosis. - *Aspergillus* species are generally considered **hyaline (clear-walled)** fungi. *Pseudohyphae with blastoconidia* - This microscopic appearance is typical of **yeasts like *Candida albicans***, which form **pseudohyphae** (elongated yeast cells that resemble hyphae) and **blastoconidia** (yeast buds). - *Aspergillus* is a mold that forms true hyphae, not pseudohyphae.

Question 468: A skin scraping from a patient with hypopigmented patches shows fungal elements on KOH mount. Which microscopic finding would confirm Malassezia furfur infection?

A. Septate hyphae
B. Short, stout hyphae with arthroconidia
C. Curved hyphae with banana-shaped macroconidia
D. Short hyphae with narrow-based budding yeast cells (Correct Answer)

Explanation: ***Short hyphae with narrow-based budding yeast cells*** - The classic "**spaghetti and meatballs**" appearance on KOH mount for *Malassezia furfur* primarily consists of **short, stubby hyphae** and clustered **budding yeast cells**, specifically with a narrow base. - This morphology is pathognomonic for **pityriasis versicolor** and related *Malassezia* infections. *Septate hyphae* - While many dermatophytes and other fungi exhibit **septate hyphae**, this term alone is too general and does not specifically identify *Malassezia furfur*. - It would not differentiate *Malassezia* from other fungal infections that also present with septate hyphae. *Short, stout hyphae with arthroconidia* - This description is more typical of **dermatophytes** like *Trichophyton* or *Epidermophyton*, which cause tinea infections. - **Arthroconidia** are characteristic asexual spores of dermatophytes, not *Malassezia furfur*. *Curved hyphae with banana-shaped macroconidia* - This morphology is characteristic of **dermatophytes** in the genus *Microsporum*, particularly *Microsporum canis*. - This finding would indicate a **tinea corporis** or **tinea capitis** infection, not a *Malassezia* infection.

Question 469: Otomycosis is most commonly caused by:

A. Mucor
B. Actinomycetes
C. Candida albicans
D. Aspergillus fumigatus (Correct Answer)

Explanation: ***Aspergillus fumigatus*** - **Aspergillus species**, particularly *A. fumigatus* and *A. niger*, are the most frequent causes of **otomycosis**, accounting for 80-90% of cases. - They thrive in damp, warm environments, making the external auditory canal an ideal site for their growth, often presenting with a **black or grayish fungal debris**. *Mucor* - **Mucor** is a less common cause of otomycosis and is more often associated with **rhinocerebral mucormycosis** in immunocompromised individuals. - While it can cause opportunistic infections, its prevalence in otomycosis is significantly lower compared to Aspergillus. *Actinomycetes* - **Actinomycetes** are **filamentous bacteria**, not fungi, and are typically associated with **actinomycosis**, a chronic suppurative infection. - They are known to cause infections in the head and neck, but not typically otomycosis, which is a fungal infection of the ear. *Candida albicans* - **Candida albicans** is the second most common cause of otomycosis, but it is less prevalent than Aspergillus species. - Infections by Candida tend to be more common in individuals with a history of **antibiotic use** or in **immunocompromised patients**, and often present with a *creamy white discharge*.

Question 470: A patient presented with some unknown fungal infection. Microscopic examination revealed brown coloured spherical fungi with septate hyphae. Possible condition:

A. Histoplasmosis
B. Candida albicans
C. Coccidioidomycosis
D. Chromoblastomycosis (Correct Answer)

Explanation: ***Chromoblastomycosis*** - This infection is characterized by the presence of **sclerotic bodies** (also known as fumagoid bodies or Medlar bodies), which are **brown-pigmented**, **spherical**, copper-colored cells or muriform cells observed in tissue. - The causative fungi, often dematiaceous molds, exhibit **septate hyphae** in culture. These molds are pigmented due to melanin in their cell walls. *Histoplasmosis* - Caused by *Histoplasma capsulatum*, which appears as **small, oval, intracellular budding yeasts** within macrophages in tissue samples. - It does not typically form sclerotic bodies or prominent septate hyphae in infected tissue. *Candida albicans* - This yeast typically presents as **ovoid budding yeast cells**, pseudohyphae, and true hyphae in tissues. - It is an **achlorophyllous** fungus, meaning it lacks pigmentation and would not appear as "brown coloured" under microscopic examination. *Coccidioidomycosis* - Caused by *Coccidioides immitis* or *C. posadasii*, which are characterized by the formation of **spherules** containing endospores in tissue. - It does not form "brown coloured spherical fungi with septate hyphae" as described; spherules are large, non-pigmented, and contain smaller endospores.

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Classification of Fungi

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Superficial Mycoses

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Dermatophytes

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Subcutaneous Mycoses

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Candidiasis

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Aspergillosis

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Cryptococcosis

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Zygomycosis

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Endemic Mycoses

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Opportunistic Fungal Infections

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Antifungal Agents

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Laboratory Diagnosis of Fungal Infections

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Mycology — MCQs

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