Mycology Practice Questions

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

Rosette of conidia. ***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*.

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

Spiral hyphae. ***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

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

Banana-shaped macroconidia. ***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*.

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

Septate hyphae with 45-degree branching. ***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.

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

Short hyphae with narrow-based budding yeast cells. ***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.

Q: Microsporum involves:

Skin and hair. ***Skin and hair*** - *Microsporum* species are **dermatophytes** that commonly cause superficial fungal infections - They have a particular predilection for keratinized tissues like **skin and hair**, leading to conditions such as **tinea capitis** (scalp ringworm) and **tinea corporis** (body ringworm) - This is the characteristic pattern for *Microsporum* species including *M. canis*, *M. audouinii*, and *M. gypseum* *Skin and nails* - While *Microsporum* can affect the skin, its involvement with **nails (onychomycosis)** is extremely rare - Nail infections are typically associated with **Trichophyton rubrum** or **T. mentagrophytes**, not *Microsporum* *Hair and nails* - **Nail involvement** is not a characteristic of *Microsporum* infections - The main sites of infection are hair and smooth skin, not nails *Skin, hair and nails* - Including **nails** as a site for *Microsporum* is inaccurate; its primary targets are skin and hair only - While some dermatophytes (like *Trichophyton*) can affect all three tissues, *Microsporum* has specific tropism for skin and hair

Q: Otomycosis is most commonly caused by:

Aspergillus fumigatus. ***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*.

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

Chromoblastomycosis. ***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.

Q: An otherwise healthy patient who has just received a prosthetic aortic valve develops postoperative fever. Blood cultures are done and she is placed on broad-spectrum antibiotics. Two days later she is still febrile and clinically deteriorating. Which of the following organisms is the most probable etiologic agent?

Candida albicans. ***Candida albicans*** - *Candida albicans* is a common cause of **early prosthetic valve endocarditis**, especially in patients with prolonged hospitalization, broad-spectrum antibiotic use, or central venous catheters [1]. - The patient's clinical deterioration despite broad-spectrum antibacterial antibiotics suggests a **fungal etiology**, as bacteria are typically covered by such therapy [2]. *Nocardia asteroides* - *Nocardia asteroides* typically causes **pulmonary or cutaneous infections** in immunocompromised individuals, less commonly endocarditis. - It would usually respond to specific antibiotics like **trimethoprim-sulfamethoxazole**, and its presentation as prosthetic valve endocarditis is rare. *Actinomyces israelii* - *Actinomyces israelii* causes **actinomycosis**, characterized by chronic, slowly progressive infections with abscesses and draining sinuses, often following oral or abdominal trauma. - While it can cause endocarditis, it is less common in the context of acute prosthetic valve infection and would likely present with a more indolent course. *Histoplasma capsulatum* - *Histoplasma capsulatum* is a **dimorphic fungus** endemic to the Ohio and Mississippi River valleys, primarily causing pulmonary infections. - Disseminated histoplasmosis with endocarditis is rare and typically occurs in immunocompromised patients, not usually in an otherwise healthy individual post-surgery.

Q: Meningitis in immunocompromised host is frequently caused by

Cryptococcus neoformans. ***Cryptococcus neoformans*** - This encapsulated yeast is **the most common cause of fungal meningitis** in **immunocompromised individuals**, particularly those with **HIV/AIDS** (CD4 count <100 cells/μL). - Infection occurs through **inhalation of spores** from pigeon droppings and soil, causing primary **pulmonary infection** before disseminating to the **CNS**. - Diagnosis: **India ink staining** shows encapsulated yeasts; **CSF cryptococcal antigen** is highly sensitive. - Classic clinical features include **subacute headache, fever, and altered mental status**. *Trichophyton rubrum* - This is a common **dermatophyte** causing **superficial fungal infections** of skin, hair, and nails (e.g., **tinea pedis**, **onychomycosis**). - It remains **confined to keratinized tissues** and does not cause invasive or systemic infections like meningitis, even in immunocompromised patients. *Epidermophyton flocculosum* - Another **dermatophyte** causing superficial infections, particularly **tinea cruris** (jock itch) and **tinea pedis**. - Like *Trichophyton rubrum*, it **cannot invade beyond the epidermis** and is not associated with deep-seated infections or meningitis. *Candida tropicalis* - While *Candida* species can cause invasive infections in immunocompromised patients, **meningitis due to *Candida tropicalis*** is **relatively rare** compared to *Cryptococcus neoformans*. - *Candida* meningitis typically occurs in **neonates, post-neurosurgical patients**, or following **candidemia**, rather than as a primary CNS infection in AIDS patients.

Question 1

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

Accepted Answer

Rosette of conidia

Answer

Flower vase arrangement

Answer

Palisading hyphae

Answer

Ship-in-bottle appearance

Question 2

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

Accepted Answer

Spiral hyphae

Answer

Microconidia in grape-like clusters

Answer

Broader angle branching

Answer

Yeast with pseudohyphae

Question 3

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

Accepted Answer

Banana-shaped macroconidia

Answer

Chlamydospores

Answer

Racquet hyphae

Answer

Ship-in-bottle appearance

Question 4

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

Accepted Answer

Septate hyphae with 45-degree branching

Answer

Broad aseptate hyphae

Answer

Dematiaceous hyphae

Answer

Pseudohyphae with blastoconidia

Question 5

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

Accepted Answer

Short hyphae with narrow-based budding yeast cells

Answer

Septate hyphae

Answer

Short, stout hyphae with arthroconidia

Answer

Curved hyphae with banana-shaped macroconidia

Question 6

Microsporum involves:

Accepted Answer

Skin and hair

Answer

Skin and nails

Answer

Hair and nails

Answer

Skin, hair and nails

Question 7

Otomycosis is most commonly caused by:

Accepted Answer

Aspergillus fumigatus

Answer

Mucor

Answer

Actinomycetes

Answer

Candida albicans

Question 8

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

Accepted Answer

Chromoblastomycosis

Answer

Histoplasmosis

Answer

Candida albicans

Answer

Coccidioidomycosis

Question 9

An otherwise healthy patient who has just received a prosthetic aortic valve develops postoperative fever. Blood cultures are done and she is placed on broad-spectrum antibiotics. Two days later she is still febrile and clinically deteriorating. Which of the following organisms is the most probable etiologic agent?

Accepted Answer

Candida albicans

Answer

Nocardia asteroides

Answer

Actinomyces israelii

Answer

Histoplasma capsulatum

Question 10

Meningitis in immunocompromised host is frequently caused by

Accepted Answer

Cryptococcus neoformans

Answer

Trichophyton rubrum

Answer

Epidermophyton flocculosum

Answer

Candida tropicalis

Mycology — MCQs

Mycology — MCQs

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