Mycology Practice Questions

Q: A plant prick can produce sporotrichosis. Which of the following statements about sporotrichosis is false?

It is an occupational disease of butchers, doctors. ***It is an occupational disease of butchers, doctors*** - Sporotrichosis is an **occupational hazard for gardeners, florists, and agricultural workers** due to exposure to decaying plant matter, not typically for butchers or doctors. - The disease is caused by **direct inoculation** of the fungus *Sporothrix schenckii* into the skin, often through a thorn prick or minor trauma. *Most cases are acquired via cutaneous inoculation* - This statement is **true** as sporotrichosis is primarily caused by **traumatic implantation** of fungal spores into the skin. - Common sources include **thorns, splinters, sphagnum moss**, and other plant materials. *Enlarged lymph nodes extending centripetally as a beaded chain are a characteristic finding* - This statement is **true** and describes the classic **lymphocutaneous sporotrichosis**, where lesions and **nodular lymphangitis** track along lymphatic channels. - The "beaded chain" appearance refers to the multiple subcutaneous nodules formed along the lymphatic vessels. *Is a chronic mycotic disease that typically involves skin, subcutaneous tissue and regional lymphatics* - This statement is **true** because sporotrichosis is a **slow-progressing fungal infection** that primarily affects the skin, the tissue just beneath the skin, and the lymphatics draining the infected area. - While systemic dissemination can occur in immunocompromised individuals, the **cutaneous and lymphocutaneous forms** are most common.

Q: Which of the following statements about Penicillium marneffei is incorrect?

Forms black colonies. ***Forms black colonies*** - *Penicillium marneffei* typically forms colonies that are often **reddish-beige** or **pigmented red-diffusible**, not black. - The production of a characteristic **red-to-burgundy pigment** is a key identifying feature of this fungus, especially in culture. *Is a dimorphic fungus* - This statement is correct. *Penicillium marneffei* is a **thermally dimorphic fungus**, meaning it grows as a mould at 25°C (room temperature) and as yeast-like cells at 37°C (body temperature). - This dimorphism is crucial for its pathogenesis and identification. *Amphotericin B is used for treatment* - This statement is correct. **Amphotericin B** is a commonly used antifungal agent for the treatment of severe *Penicillium marneffei* infections, particularly in immunocompromised patients. - It is often followed by a maintenance regimen with an azole antifungal like itraconazole. *Causes severe infections in immunocompromised patients* - This statement is correct. *Penicillium marneffei* is an **opportunistic pathogen** that primarily causes severe, disseminated infections in individuals with compromised immune systems, especially those with HIV/AIDS. - Endemic regions include Southeast Asia, where it is a leading cause of systemic mycosis in HIV-positive patients.

Q: In a patient presenting with respiratory symptoms, acute angled septate hyphae are seen in which of the following fungi?

Aspergillus. ***Aspergillus*** - *Aspergillus* species are characterized by their distinctive **acute-angled (dichotomous) septate hyphae** when observed microscopically in tissue sections or clinical samples. - This morphological feature is crucial for differentiating *Aspergillus* infections, such as **aspergillosis**, from other fungal infections. *Mucor* - *Mucor* (along with *Rhizopus* and *Lichtheimia*) belongs to the Zygomycetes class, which are characterized by **broad, non-septate, ribbon-like hyphae** with irregular branching, not acute-angled septate hyphae. - These fungi are associated with **mucormycosis**, often seen in immunocompromised patients, particularly those with diabetes. *Penicillium* - *Penicillium* is a common mold known for producing penicillin and typically appears as **septate hyphae** but is more often recognized by its branching, brush-like conidiophores (penicilli) in culture rather than a distinct acute-angled septate hyphal morphology in clinical samples causing invasive disease. - While it can cause opportunistic infections, its hyphae are less commonly described as having uniquely acute angles compared to *Aspergillus*. *Candida* - *Candida* species are typically observed as **yeast cells (oval budding forms)**, often forming **pseudohyphae** (elongated yeast cells that remain attached) or true hyphae under specific conditions, but not as acute-angled septate hyphae. - *Candida* is a common cause of superficial and invasive candidiasis, and its microscopic appearance is distinct from filamentous fungi.

Q: Which fungus is commonly known as golden yellow jelly fungus?

Tremella mesenterica. ***Tremella mesenterica*** - This fungus is commonly referred to as **golden yellow jelly fungus** or **witch's butter** due to its distinctive golden-yellow, gelatinous, and brain-like appearance. - It is a **jelly fungus** that typically grows on dead hardwood branches, especially after rain, and is known for its pliable, quivering texture. *T. tonsurans* - This refers to **Trichophyton tonsurans**, a dermatophytic fungus primarily known for causing **tinea capitis** (ringworm of the scalp). - Its common name relates to its effect on hair, causing breakage and a "black dot" appearance, rather than a golden yellow, jelly-like form. *Epidermophyton floccosum* - This is a dermatophytic fungus that specifically causes infections of the **skin and nails**, particularly **tinea pedis** (athlete's foot) and **tinea cruris** (jock itch). - It does not produce a fruiting body and is not described as a jelly-like fungus. *T. mentagrophytes* - This refers to **Trichophyton mentagrophytes**, another common dermatophyte responsible for various superficial fungal infections, including **tinea pedis**, **tinea corporis**, and **tinea unguium**. - Its clinical presentation is not that of a golden yellow jelly fungus.

Q: Which of the following fungi is primarily responsible for causing Tinea cruris?

Trichophyton rubrum. ***Trichophyton rubrum*** - **Trichophyton rubrum** is the **most common dermatophyte** responsible for causing **Tinea cruris**, also known as **jock itch**, accounting for approximately 80-90% of cases. - This fungus thrives in warm, moist environments, making the groin area an ideal site for infection. - It is the **primary causative agent** worldwide for this condition. *Epidermophyton floccosum* - While **Epidermophyton floccosum** can cause **Tinea cruris**, it is significantly less common than **Trichophyton rubrum**, accounting for approximately 10-20% of cases. - It is also known to cause **Tinea pedis** (athlete's foot) and onychomycosis. *Microsporum canis* - **Microsporum canis** is a common cause of **Tinea capitis** (ringworm of the scalp) and **Tinea corporis** (ringworm of the body), particularly in children. - It is primarily transmitted from **infected animals**, especially cats and dogs, to humans and is **rarely implicated in Tinea cruris**. *None of the options* - This option is incorrect because **Trichophyton rubrum** is the well-established and primary cause of **Tinea cruris**. - At least one of the listed options is a recognized pathogen for this condition.

Q: Which of the following Trichophyton species is known to be zoophilic?

T. mentagrophytes. ***T. mentagrophytes*** - This species is well-known for being **zoophilic**, meaning it primarily infects animals but can be transmitted to humans. - It is a common cause of **tinea corporis** (ringworm of the body), **tinea pedis** (athlete's foot), and **tinea barbae**, often contracted from contact with infected pets or farm animals. *T. tonsurans* - This is an **anthropophilic** species, meaning it primarily infects humans. - It is a leading cause of **tinea capitis** (ringworm of the scalp) in the United States, particularly among children, and typically presents with a "black dot" appearance. *T. violaceum* - This is another **anthropophilic** species, endemic in various parts of the world, especially the Middle East and Africa. - It also causes **tinea capitis** and can lead to a characteristic "gray patch" type of infection. *T. schoenleinii* - This is an **anthropophilic** species historically associated with **favus**, a severe form of tinea capitis. - Favus is characterized by the formation of sulfur-yellow, cup-shaped crusts called **scutula** and can lead to permanent hair loss and scarring.

Q: Which of the following is the most common yeast pathogen?

Candida. ***Candida*** - **Candida** species, particularly *Candida albicans*, are the **most common cause of fungal infections** worldwide, ranging from superficial mucocutaneous infections to invasive systemic candidiasis. - They are part of the normal human microbiota and opportunistic pathogens, thriving in conditions like **immunocompromise**, antibiotic use, or presence of medical devices. *Mucor* - **Mucor** is a genus of mold, not yeast, and is known to cause **mucormycosis**, a severe and rapidly progressive fungal infection. - While dangerous, mucormycosis is **much rarer** compared to candidiasis. *Rhizopus* - **Rhizopus** is also a genus of mold, not yeast, and is another causative agent of **mucormycosis**, particularly in immunocompromised individuals. - Like Mucor, infections caused by Rhizopus are **less common** than those caused by Candida. *Cryptococcus* - **Cryptococcus neoformans** is a significant yeast pathogen, primarily causing **cryptococcosis**, which often manifests as meningoencephalitis in immunocompromised patients. - Although it is an important pathogen, its overall incidence is **lower than that of Candida** species.

Q: Aseptate hyphae is not seen in which of the following fungi?

Aspergillus. ***Correct: Aspergillus*** - *Aspergillus* species are characterized by **septate hyphae** and **acute angle branching**, distinguishing them from zygomycetes. - They cause diseases such as **allergic bronchopulmonary aspergillosis (ABPA)**, aspergilloma, and invasive aspergillosis. - Since Aspergillus has septate hyphae, **aseptate hyphae are NOT seen** in Aspergillus. *Incorrect: Rhizopus* - *Rhizopus* is a zygomycete with **broad, ribbon-like, aseptate hyphae** and **right-angle/irregular branching**. - Common cause of **mucormycosis (zygomycosis)**, especially in immunocompromised individuals. *Incorrect: Mucor* - *Mucor* is another zygomycete with **aseptate hyphae** and **wide-angle branching**. - Causes mucormycosis, leading to severe infections primarily in patients with **diabetic ketoacidosis** or **hematologic malignancies**. *Incorrect: Penicillium* - *Penicillium* species possess **septate hyphae** with characteristic **brush-like (penicillus-shaped)** fruiting bodies. - While some produce antibiotics, certain species like *Talaromyces marneffei* can cause systemic infections in immunocompromised patients.

Q: Regarding fungal cell wall, all are true except:

Azoles act on them. ***Azoles act on them*** - **Azole antifungals** primarily target the **ergosterol synthesis** pathway, specifically inhibiting the **lanosterol 14-alpha-demethylase** enzyme, which is located in the fungal cell membrane, not the cell wall. - While the cell wall is crucial for fungal viability, agents targeting it (e.g., **echinocandins**) are distinct from azoles. *Contains chitin* - The fungal cell wall is indeed a complex structure composed of various carbohydrates, with **chitin** being a major structural polysaccharide that provides rigidity. - Chitin is a **beta-(1,4)-linked polymer of N-acetylglucosamine** and is a unique component distinguishing fungal cells from animal cells. *Prevent osmotic damage* - The rigid fungal cell wall provides structural support and protects the cell from **environmental stresses**, particularly **osmotic lysis** in hypotonic environments. - It maintains the cell's integrity against internal **turgor pressure**, which is essential for fungal growth and survival. *Does not contain peptidoglycan* - Fungal cell walls are distinct from bacterial cell walls in their composition; they **do not contain peptidoglycan**. - **Peptidoglycan** is a characteristic component of bacterial cell walls, which is targeted by antibiotics like penicillins.

Q: Which of the following is NOT a virulence factor of Cryptococcus?

Production of protease. ***Production of protease*** - While *Cryptococcus neoformans* can produce some proteolytic enzymes, **protease production is not considered a major or classical virulence factor** in standard medical microbiology literature. - Unlike the other three factors listed, proteases are not prominently featured as key virulence mechanisms in *Cryptococcus* pathogenesis for medical education purposes. - The primary virulence factors emphasized for *Cryptococcus* are the capsule, melanin, and urease. *Polysaccharide capsule* - The **polysaccharide capsule** is the MOST important virulence factor, protecting the yeast from phagocytosis and immune clearance. - It interferes with antigen presentation, antibody binding, and complement activation, making it crucial for survival in the host. *Ability to make melanin* - **Melanin production** protects *Cryptococcus* from oxidative stress, free radicals, UV radiation, and antifungal agents. - It contributes to survival in macrophages and persistence in the central nervous system. *Urease production* - **Urease production** enables *Cryptococcus* to cross the blood-brain barrier and colonize the central nervous system. - Urease hydrolyzes urea into ammonia, causing local alkalinization that facilitates CNS invasion and contributes to meningoencephalitis.

Question 1

A plant prick can produce sporotrichosis. Which of the following statements about sporotrichosis is false?

Accepted Answer

It is an occupational disease of butchers, doctors

Answer

Enlarged lymph nodes extending centripetally as a beaded chain are a characteristic finding

Answer

Most cases are acquired via cutaneous inoculation

Answer

Is a chronic mycotic disease that typically involves skin, subcutaneous tissue and regional lymphatics

Question 2

Which of the following statements about Penicillium marneffei is incorrect?

Accepted Answer

Forms black colonies

Answer

Is a dimorphic fungus

Answer

Amphotericin B is used for treatment

Answer

Causes severe infections in immunocompromised patients

Question 3

In a patient presenting with respiratory symptoms, acute angled septate hyphae are seen in which of the following fungi?

Accepted Answer

Aspergillus

Answer

Mucor

Answer

Penicillium

Answer

Candida

Question 4

Which fungus is commonly known as golden yellow jelly fungus?

Accepted Answer

Tremella mesenterica

Answer

T. tonsurans

Answer

Epidermophyton floccosum

Answer

T. mentagrophytes

Question 5

Which of the following fungi is primarily responsible for causing Tinea cruris?

Accepted Answer

Trichophyton rubrum

Answer

Microsporum canis

Answer

Epidermophyton floccosum

Answer

None of the options

Question 6

Which of the following Trichophyton species is known to be zoophilic?

Accepted Answer

T. mentagrophytes

Answer

T. tonsurans

Answer

T. violaceum

Answer

T. schoenleinii

Question 7

Which of the following is the most common yeast pathogen?

Accepted Answer

Candida

Answer

Mucor

Answer

Rhizopus

Answer

Cryptococcus

Question 8

Aseptate hyphae is not seen in which of the following fungi?

Accepted Answer

Aspergillus

Answer

Rhizopus

Answer

Mucor

Answer

Penicillium

Question 9

Regarding fungal cell wall, all are true except:

Accepted Answer

Azoles act on them

Answer

Contains chitin

Answer

Prevent osmotic damage

Answer

Does not contain peptidoglycan

Question 10

Which of the following is NOT a virulence factor of Cryptococcus?

Accepted Answer

Production of protease

Answer

Polysaccharide capsule

Answer

Ability to make melanin

Answer

Urease production

Mycology — MCQs

Mycology — MCQs

On this page

Practice by Chapter

Want unlimited practice?