Mycology Practice Questions

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.

Q: Pityriasis versicolor is caused by

Malassezia furfur. ***Malassezia furfur*** - **Pityriasis versicolor** is a superficial fungal infection caused by yeasts of the genus **Malassezia**, with **_Malassezia furfur_** being the most common species implicated. - This fungus normally resides on the skin but can overgrow under certain conditions (e.g., heat, humidity, oily skin), leading to characteristic **discolored patches**. *T. rubrum* - **_T. rubrum_** (Trichophyton rubrum) is a common **dermatophyte** responsible for various tinea infections, such as tinea pedis (**athlete's foot**) and tinea cruris (**jock itch**). - It causes infections in the **keratinized tissues** (skin, hair, nails) but is not the causative agent of pityriasis versicolor. *Candida species* - **_Candida_ species**, particularly **_Candida albicans_**, are yeasts that commonly cause **candidiasis** (e.g., oral thrush, vaginal yeast infections, diaper rash). - These infections typically present with **erythematous** and **pruritic** lesions, often in immunocompromised individuals or in moist body folds, which differs from pityriasis versicolor. *E. floccosum* - **_E. floccosum_** (Epidermophyton floccosum) is another **dermatophyte** primarily associated with infections of the skin and nails, causing conditions like **tinea pedis**, tinea cruris, and **onychomycosis**. - It does not cause pityriasis versicolor; this genus specifically attacks **superficial keratinized structures** and lacks the ability to invade living tissues.

Q: Which of the following is a false statement about the respective fungal infections?

Microsporium involves nail. ***Microsporium involves nail*** - This statement is considered **false** for exam purposes because *Microsporum* species are **NOT primary causes** of **tinea unguium** (onychomycosis). - *Microsporum* species primarily cause **tinea capitis** (scalp ringworm) and **tinea corporis** (body ringworm). While rare cases of nail involvement have been reported, it is clinically insignificant. - **Tinea unguium** (onychomycosis) is predominantly caused by ***Trichophyton rubrum*** and ***Trichophyton mentagrophytes***, with *Epidermophyton floccosum* and *Candida* species also playing roles. *Superficial layers of skin are involved* - This is a **true statement** because dermatophyte infections generally affect the **stratum corneum**, hair, and nails, which are all superficial keratinized tissues. - These fungi are unable to penetrate deeper viable tissue due to their inability to grow at core body temperature and the presence of inhibitory factors in serum. *Candida albicans causes skin infection* - This is a **true statement** as *Candida albicans* is a common cause of **cutaneous candidiasis**, manifesting as intertrigo, diaper rash, and paronychia. - It thrives in warm, moist environments and can infect skin folds, mucous membranes, and damaged skin. *Epidermophyton doesn't involve hair* - This is a **true statement** because *Epidermophyton floccosum* is unique among dermatophytes in that it primarily causes infections of the **skin** (tinea corporis, tinea cruris, tinea pedis) and **nails** (onychomycosis) but **does not infect hair follicles**. - Unlike *Trichophyton* and *Microsporum*, *Epidermophyton* lacks the enzymatic machinery to invade hair shafts.

Q: Thrush refers to

Acute pseudomembranous candidiasis. ***Acute pseudomembranous candidiasis*** - **Thrush** is the common term for **acute pseudomembranous candidiasis**, characterized by creamy white, cottage cheese-like plaques on the oral mucosa that can be scraped off [1]. - It is typically caused by **Candida albicans** and often seen in infants, immunocompromised individuals, or those using antibiotics or corticosteroids [1]. *Acute atrophic candidiasis* - This form presents as a **red, raw, and painful** area, often after antibiotic use, and does not have the classic white plaques associated with thrush. - It involves mucosal thinning and inflammation due to fungal overgrowth, lacking the pseudomembrane. *Chronic atrophic candidiasis* - Often associated with **denture wearers** (denture stomatitis) and appears as erythema and edema beneath the denture, without significant white lesions. - It is a persistent inflammation and redness of the mucosa due to chronic candidal infection under an ill-fitting or poorly cleaned denture. *Chronic hyperplastic candidiasis* - This is a less common form characterized by **non-scrapable white lesions** that can appear nodular or homogeneous and are often considered potentially malignant. - It involves fungal invasion into the deeper layers of the epithelium, leading to hyperkeratosis and epithelial hyperplasia, making the lesions firmly adherent.

Q: Which of the following is NOT a fungal infection?

Mycoses fungoides. ***Mycoses fungoides*** - This is a type of **cutaneous T-cell lymphoma**, which is a **malignancy of lymphocytes**, not a fungal infection [1]. - It presents with skin lesions that can mimic various dermatological conditions but is characterized by abnormal T-cells infiltrating the skin [1], [2]. *Black Piedra* - This is a superficial fungal infection of the **hair shaft** caused by **Piedraia hortae**, forming hard, black nodules. - It is an example of a **dermatomycosis**. *White Piedra* - This is a fungal infection of the **hair shaft** caused by **Trichosporon species**, leading to soft, white to light brown nodules. - Like black piedra, it is also a **dermatomycosis**. *Tinea nigra Palmaris* - This is a superficial fungal infection of the **stratum corneum** of the skin, primarily on the palms and soles, caused by **Hortaea werneckii**. - It presents as irregular, darkly pigmented (brown to black) macules and is a true **mycosis**. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of White Blood Cells, Lymph Nodes, Spleen, and Thymus, pp. 613-614. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Diseases Of The Urinary And Male Genital Tracts, pp. 564-565.

Q: 'Pityriasis versicolor' is caused by:

Malassezia furfur. ***Malassezia furfur*** - **Pityriasis versicolor** is a superficial fungal infection of the skin caused by the dimorphic yeast **Malassezia furfur** (also known as Pityrosporum ovale). - This organism is part of the normal skin flora but can become pathogenic under certain conditions, leading to characteristic **hypopigmented or hyperpigmented patches**, often on the trunk. *Nocardia species* - **Nocardia** are aerobic, gram-positive bacteria that typically cause **pulmonary, cutaneous, or disseminated infections**, particularly in immunocompromised individuals. - They are known for causing conditions like **nocardiosis**, which presents with abscesses, not pityriasis versicolor. *Aspergillus fumigatus* - **Aspergillus fumigatus** is a common mold that can cause a range of diseases, primarily in the respiratory tract, including **allergic bronchopulmonary aspergillosis (ABPA)**, **aspergilloma**, and **invasive aspergillosis**. - It is not associated with superficial skin infections like pityriasis versicolor. *Trichophyton rubrum* - **Trichophyton rubrum** is a dermatophyte fungus that commonly causes **tinea (ringworm) infections** of the skin, hair, and nails, such as **athlete's foot (tinea pedis)**, **jock itch (tinea cruris)**, and **nail infections (onychomycosis)**. - Unlike Malassezia, it invades the keratinized structures of the epidermis, not just superficial layers causing versicolor lesions.

Q: A patient from the Ohio River valley presents with granulomatous prostatitis showing broad-based budding organisms on microscopy. What is the most likely infecting organism?

Blastomyces dermatitidis. ***Blastomyces dermatitidis*** - This organism is endemic to the **Ohio River valley** and is known to cause **granulomatous inflammation**, including in the prostate. - Its characteristic morphology is **broad-based budding yeast** on microscopy, fitting the description. *Escherichia coli* - While *E. coli* is a common cause of **bacterial prostatitis**, it does not present as granulomatous inflammation. - It is a **bacterium**, not a fungus, and would not show broad-based budding organisms. *Histoplasma capsulatum* - **Histoplasma** is also endemic to the Ohio River valley and causes granulomatous disease, but its yeast forms are **small**, intracellular, and do not exhibit broad-based budding. - It is often associated with a history of exposure to **bat or bird droppings** and commonly affects the lungs. *Pseudomonas aeruginosa* - *Pseudomonas aeruginosa* causes **bacterial infections**, often in immunocompromised individuals or associated with catheter use, and is not a fungus. - It causes **acute inflammation**, not chronic granulomatous inflammation, and does not show broad-based budding.

Q: Medlar bodies are found in -

Chromoblastomycosis. ***Chromoblastomycosis*** - **Medlar bodies**, also known as **sclerotic bodies** or **copper pennies**, are thick-walled, septate, dematiaceous fungal cells characteristic of chromoblastomycosis. - They are typically found within **giant cells** or extracellularly in the dermis during histological examination of infected tissue. *Mycetoma* - Characterized by the presence of **grains** or **granules** composed of aggregated fungal hyphae (eumycetoma) or bacterial filaments (actinomycetoma) within the tissue [2]. - It presents as a chronic, progressive infection involving the skin, subcutaneous tissue, and often underlying bone [2]. *Histoplasmosis* - Caused by **_Histoplasma capsulatum_**, a dimorphic fungus that appears as small, oval, budding yeast cells within **macrophages** in infected tissues [1]. - It primarily affects the lungs but can disseminate to other organs, especially in immunocompromised individuals [1]. *Sporotrichosis* - Caused by **_Sporothrix schenckii_**, which appears as small, cigar-shaped budding yeast forms or asteroid bodies (yeast cells surrounded by an eosinophilic cuticle) in tissue. - It typically presents as **lymphocutaneous lesions** following traumatic inoculation of fungal spores [2]. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Lung, p. 717. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Infectious Diseases, pp. 393-394.

Question 1

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 2

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 3

Meningitis in immunocompromised host is frequently caused by

Accepted Answer

Cryptococcus neoformans

Answer

Trichophyton rubrum

Answer

Epidermophyton flocculosum

Answer

Candida tropicalis

Question 4

Pityriasis versicolor is caused by

Accepted Answer

Malassezia furfur

Answer

T. rubrum

Answer

Candida species

Answer

E. floccosum

Question 5

Which of the following is a false statement about the respective fungal infections?

Accepted Answer

Microsporium involves nail

Answer

Superficial layers of skin are involved

Answer

Candida albicans causes skin infection

Answer

Epidermophyton doesn't involve hair

Question 6

Thrush refers to

Accepted Answer

Acute pseudomembranous candidiasis

Answer

Acute atrophic candidiasis

Answer

Chronic atrophic candidiasis

Answer

Chronic hyperplastic candidiasis

Question 7

Which of the following is NOT a fungal infection?

Accepted Answer

Mycoses fungoides

Answer

Black Piedra

Answer

White Piedra

Answer

Tinea nigra Palmaris

Question 8

'Pityriasis versicolor' is caused by:

Accepted Answer

Malassezia furfur

Answer

Nocardia species

Answer

Aspergillus fumigatus

Answer

Trichophyton rubrum

Question 9

A patient from the Ohio River valley presents with granulomatous prostatitis showing broad-based budding organisms on microscopy. What is the most likely infecting organism?

Accepted Answer

Blastomyces dermatitidis

Answer

Escherichia coli

Answer

Histoplasma capsulatum

Answer

Pseudomonas aeruginosa

Question 10

Medlar bodies are found in -

Accepted Answer

Chromoblastomycosis

Answer

Mycetoma

Answer

Histoplasmosis

Answer

Sporotrichosis

Mycology — MCQs

Mycology — MCQs

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