Mycology Practice Questions

Q: The most common cause of bronchopulmonary aspergillosis is

Aspergillus fumigatus. ***Aspergillus fumigatus*** - This species is the **most common cause** of pulmonary aspergillosis, including allergic bronchopulmonary aspergillosis (ABPA), due to its ubiquitous presence and ability to grow at human body temperature. - It produces **small spores** that can easily reach the lower airways and trigger allergic or invasive responses in susceptible individuals. *Aspergillus clavatus* - This species is less commonly implicated in human disease and is more typically associated with **occupational exposures**, such as in malting barley factories, leading to extrinsic allergic alveolitis. - It is **not a primary cause** of bronchopulmonary aspergillosis in the general population. *Aspergillus niger* - While *A. niger* can cause **otomycosis** and occasionally **aspergilloma**, it is a far less common cause of allergic bronchopulmonary aspergillosis compared to *A. fumigatus*. - It is known for producing black spores, which can sometimes be seen in fungal balls, but its role in pulmonary allergic disease is limited. *Aspergillus flavus* - *A. flavus* is primarily known for producing **aflatoxins** and is more commonly associated with **invasive aspergillosis** in immunocompromised patients, particularly in tropical and subtropical regions. - It is **not the leading cause** of allergic bronchopulmonary aspergillosis.

Q: A 27-year-old intravenous drug user presents with difficulty swallowing. Examination of the oropharynx reveals white plaques along the tongue and the oral mucosa. Which of the following best describes the microscopic appearance of the microorganism responsible for this patient's illness?

Budding yeast and pseudohyphae. ***Budding yeast and pseudohyphae*** - The clinical presentation of **white plaques** in the oropharynx of an **IV drug user** strongly suggests **oral candidiasis** (thrush), caused by *Candida albicans*. - Microscopically, *Candida albicans* is characterized by **budding yeast** forms and the formation of **pseudohyphae** when invading tissues. *Encapsulated yeast* - This description typically refers to *Cryptococcus neoformans*, which is known for its **thick polysaccharide capsule**. - While *Cryptococcus* can cause infections in immunocompromised individuals, it typically presents with **meningitis** or **pulmonary disease**, not oral thrush. *Mold with nonseptate hyphae* - This morphology is characteristic of organisms causing **zygomycosis** (e.g., *Rhizopus*, *Mucor*). - These infections usually present as **rhinocerebral** or **pulmonary involvement** and are not associated with superficial oral plaques like those seen in this patient. *Mold with septate hyphae* - This describes many common molds, including *Aspergillus* species, which typically cause **invasive pulmonary disease**, **sinusitis**, or **allergic bronchopulmonary aspergillosis**. - These organisms are **not typically associated** with oral thrush and produce true hyphae with septations, unlike the pseudohyphae of *Candida*.

Q: Claviceps purpurea produces which of the following toxins?

Ergot alkaloids. ***Ergot alkaloids*** - **Claviceps purpurea** is a fungus that infects cereals, particularly rye, and produces a group of toxic compounds known as **ergot alkaloids**. - These alkaloids can cause a condition called **ergotism**, which includes symptoms like hallucinations, gangrene, and severe vasoconstriction. *Aflatoxins* - **Aflatoxins** are produced by species of **Aspergillus fungi**, such as *A. flavus* and *A. parasiticus*, not *Claviceps purpurea*. - They are potent **carcinogens** and are commonly found in contaminated crops like peanuts and maize. *Sanguinarine alkaloid* - **Sanguinarine** is an alkaloid derived from plants like **bloodroot (Sanguinaria canadensis)**, not *Claviceps purpurea*. - It has been linked to **glaucoma** and liver toxicity. *Pyrazolidone drug* - **Pyrazolidone** is a classification of synthetic drugs, often used as **non-steroidal anti-inflammatory drugs (NSAIDs)**, such as phenylbutazone. - This is a pharmaceutical compound and not naturally derived from *Claviceps purpurea* or any fungus.

Q: Tinea corporis is commonly caused by all the following except which one?

C. albicans. ***C. albicans*** - **_Candida albicans_** is typically associated with **mucocutaneous candidiasis** (e.g., thrush, vaginal yeast infections, intertrigo) and **invasive candidiasis**, not with tinea corporis. - Tinea corporis is caused by **dermatophytes**, which are fungi that specifically infect keratinized tissues, while _C. albicans_ is a yeast that can colonize and infect various body sites. *T. rubrum* - **_Trichophyton rubrum_** is one of the most common causes of **dermatophyte infections** worldwide, including tinea corporis, tinea pedis, and onychomycosis. - It is a **dermatophyte** known for its chronic and often inflammatory presentations in skin infections. *E. floccosum* - **_Epidermophyton floccosum_** is another significant dermatophyte that frequently causes **tinea corporis**, tinea cruris (jock itch), and tinea pedis (athlete's foot). - It is characterized by its ability to exclusively infect skin and nails, not hair. *M. canis* - **_Microsporum canis_** is a common cause of **tinea corporis**, especially in children, and is often acquired from **infected animals** like cats and dogs. - It is a **zoophilic dermatophyte** that typically causes inflammatory lesions on the skin and can also cause tinea capitis.

Q: Bodies characteristic of chromoblastomycosis, also known as Medlar bodies, are typically found in which of the following?

Sclerotic bodies. #### ***Sclerotic bodies*** * These are **dark brown, spherical, thick-walled fungi cells** that divide by septation, rather than budding. * They are often referred to as **Medlar bodies** or **muriform cells**, and their presence is diagnostic of **chromoblastomycosis**. #### *Asteroid bodies* * These are **eosinophilic star-like structures** found in granulomas, typically seen in **sporotrichosis** around fungal cells. * They are formed by the deposition of **antigen-antibody complexes** and host proteins on the surface of the fungal organism. #### *Torres bodies* * These are **eosinophilic intracytoplasmic inclusions** found in the neurons of the **hippocampus** and **cerebellum** in cases of **rabies**. * Their presence is a definitive diagnostic feature of rabies in affected brain tissue. #### *Guarnieri bodies* * These are **eosinophilic intracytoplasmic inclusions** seen in cells infected with **variola (smallpox) virus**. * They are characteristic of **poxvirus infections** and represent viral factories where replication occurs.

Q: The germ tube test is done for:

Candida albicans. ***Candida albicans*** - The **germ tube test** is a rapid screening method used to differentiate *Candida albicans* from other *Candida* species and yeasts. - *Candida albicans* produces **germ tubes** (true hyphae without constrictions at the base) when incubated in serum at 37°C for 2-3 hours. *Chlamydia* - **Chlamydia** species are **obligate intracellular bacteria** and are identified using molecular methods (e.g., NAAT), culture, or immunofluorescence, not the germ tube test. - They do not form structures like germ tubes, as they are prokaryotic organisms. *Bacterial vaginosis* - **Bacterial vaginosis** is a dysbiosis of the vaginal flora, diagnosed based on Amsel criteria (e.g., clue cells, pH >4.5, positive whiff test) or Nugent score from Gram stain. - It involves an overgrowth of various anaerobic bacteria and a decrease in lactobacilli, none of which produce germ tubes. *Neisseria gonorrhoeae* - **Neisseria gonorrhoeae** is a Gram-negative bacterium, typically identified by Gram stain showing intracellular **Gram-negative diplococci** within neutrophils, and subsequent culture or NAAT. - As a bacterium, it does not form germ tubes; this test is specific to certain fungi.

Q: Which of the following is the causative agent of Favus?

Trichophyton schoenleinii. ***Trichophyton schoenleinii*** - This fungus is the classic causative agent of **Favus**, a severe form of tinea capitis characterized by **sulfur-yellow cup-shaped crusts** called scutula. - Favus often leads to **permanent scarring alopecia** due to follicular destruction. *Microsporum audouinii* - This species is a common cause of **epidemic tinea capitis** in children, particularly in schools. - It typically causes **gray patch tinea capitis**, characterized by scaly patches and broken hairs, but not scutula. *Microsporum canis* - *M. canis* is a **zoophilic fungus**, commonly transmitted to humans from infected cats and dogs. - It is a frequent cause of **inflammatory tinea capitis** and tinea corporis, presenting with scaling, erythema, and occasional pustules. *Trichophyton mentagrophytes* - This dermatophyte can cause various forms of tinea, including **tinea pedis (athlete's foot)**, tinea cruris, and highly inflammatory tinea capitis or barbae. - It is known for causing both **inflammatory and non-inflammatory lesions**, but not specifically Favus.

Question 1

The most common cause of bronchopulmonary aspergillosis is

Accepted Answer

Aspergillus fumigatus

Answer

Aspergillus niger

Answer

Aspergillus clavatus

Answer

Aspergillus flavus

Question 2

A 27-year-old intravenous drug user presents with difficulty swallowing. Examination of the oropharynx reveals white plaques along the tongue and the oral mucosa. Which of the following best describes the microscopic appearance of the microorganism responsible for this patient's illness?

Accepted Answer

Budding yeast and pseudohyphae

Answer

Encapsulated yeast

Answer

Mold with nonseptate hyphae

Answer

Mold with septate hyphae

Question 3

Claviceps purpurea produces which of the following toxins?

Accepted Answer

Ergot alkaloids

Answer

Aflatoxins

Answer

Sanguinarine alkaloid

Answer

Pyrazolidone drug

Question 4

Tinea corporis is commonly caused by all the following except which one?

Accepted Answer

C. albicans

Answer

M. canis

Answer

T. rubrum

Answer

E. floccosum

Question 5

Bodies characteristic of chromoblastomycosis, also known as Medlar bodies, are typically found in which of the following?

Accepted Answer

Sclerotic bodies

Answer

Asteroid bodies

Answer

Torres bodies

Answer

Guarnieri bodies

Question 6

The germ tube test is done for:

Accepted Answer

Candida albicans

Answer

Neisseria gonorrhoeae

Answer

Bacterial vaginosis

Answer

Chlamydia

Question 7

Which of the following is the causative agent of Favus?

Accepted Answer

Trichophyton schoenleinii

Answer

Microsporum audouinii

Answer

Trichophyton mentagrophytes

Answer

Microsporum canis

Mycology — MCQs

Mycology — MCQs

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