MYCOLOGY MCQs — Complete Bank

Question 1

An organism without a known sexual stage of reproduction would be classified in which of the following fungal groups?

Accepted Answer

Mitosporic fungi — Fungi with no known sexual stage are classified as Fungi Imperfecti (Deuteromycota/Mitosporic fungi). They reproduce exclusively through asexual means via mitosis, producing conidia. Examples include Candida and Aspergillus species in their imperfect forms.

Question 2

An antifungal drug such as Miconazole inhibits proper formation of which cellular component?

Accepted Answer

Plasma membrane formation — Miconazole is an azole antifungal that inhibits the enzyme lanosterol 14-α-demethylase, blocking ergosterol biosynthesis and disrupting the fungal plasma membrane.

Question 3

Which of the following fungi would you most likely find growing in pigeon droppings?

Accepted Answer

Cryptococcus — Cryptococcus neoformans thrives in soil enriched by pigeon and bird droppings. The nitrogen-rich guano provides ideal growth conditions.

Question 4

Which fungal condition causes more than 200 million cases per year worldwide, with symptoms including an itching sensation and burning internal pain?

Accepted Answer

Vulvovaginitis — Vulvovaginal candidiasis caused by Candida albicans is among the most common fungal infections globally. Symptoms include vaginal itching, burning, and discharge.

Question 5

The formation of arthrospores and spherules in infected tissue is characteristic of which fungal disease?

Accepted Answer

Coccidioidomycosis — Coccidioides immitis uniquely produces arthrospores in soil and spherules filled with endospores in tissue. This dimorphic characteristic is pathognomonic for Coccidioidomycosis (Valley Fever).

Question 6

Aflatoxin is produced by which organism, and what type of substance is it?

Accepted Answer

Aspergillus flavus — Carcinogen — Aflatoxin is produced by Aspergillus flavus and A. parasiticus . It is a potent hepatocarcinogen that contaminates food.

Question 7

A girl who pricked her finger while pruning rose bushes develops a local pustule that progresses to an ulcer. Several nodules then develop along the local lymphatic drainage. What is the most likely causative agent?

Accepted Answer

Sporothrix schenckii — This is the classic presentation of Sporotrichosis ('Rose Gardener's Disease'), caused by Sporothrix schenckii , which spreads in a characteristic lymphocutaneous pattern.

Question 8

Fungal cells that reproduce by budding are seen in the infected tissues of patients with which of the following combinations?

Accepted Answer

Candidiasis, cryptococcosis, and sporotrichosis — All three pathogens ( Candida , Cryptococcus , Sporothrix ) exist as budding yeast forms in host tissue at 37°C.

Question 9

Which of the following statements regarding paracoccidioidomycosis is NOT correct?

Accepted Answer

The etiologic agent is inherently resistant to amphotericin B — Paracoccidioides brasiliensis is not inherently resistant to amphotericin B; it is an effective treatment for severe cases. The other statements are correct.

Question 10

A kidney transplant patient develops nosocomial systemic candidiasis. The isolated Candida glabrata strain is resistant to fluconazole. What is the most reasonable oral alternative?

Accepted Answer

Posaconazole — Candida glabrata is notorious for azole resistance. Posaconazole is a broad-spectrum extended triazole effective against fluconazole-resistant strains and is available orally.

Question 11

All of the following are characteristics of systemic mycoses (deep mycoses) EXCEPT:

Accepted Answer

The most common body part is the lungs for ALL fungal infections — The lungs are not the site for ALL fungal infections; some, like sporotrichosis and mycetoma, enter through the skin.

Question 12

Thousands of people in the western USA suddenly developed flu-like symptoms and pneumonia in 1992. The causative agent was found to be fungal spores in soil and air, causing fever, cough, and fatigue. The disease was termed Valley Fever. What is the pathogen?

Accepted Answer

Coccidioides immitis — Valley Fever is caused by Coccidioides immitis , endemic to the southwestern USA, where inhaled arthrospores from soil cause acute pulmonary infection.

Question 13

Which pathogen isolated from a sputum specimen shows mold growth with tuberculate macroconidia and oval microconidia in laboratory culture?

Accepted Answer

Histoplasma capsulatum — The mold phase of Histoplasma capsulatum is characterized by large tuberculate macroconidia and smaller oval microconidia.

Question 14

The fungi Trichosporon commonly causes superficial infection of hair called white piedra. Which species of Trichosporon specifically causes scalp hair white piedra?

Accepted Answer

Trichosporon ovoides — Trichosporon ovoides is the species that specifically causes white piedra on scalp hair.

Question 15

A 26-year-old man develops itchy, white flaky, and stinging patches between the toe webs and soles of the feet. The infection is characterized by inflammation and skin fissures. Which is the most likely etiological agent?

Accepted Answer

Trichophyton rubrum — This describes Tinea pedis (Athlete's Foot), with Trichophyton rubrum being the most common cause worldwide, characterized by chronic interdigital infections.

Question 16

Which of the following best describes the lesion characteristics of Pityriasis Versicolor?

Accepted Answer

Hypopigmented and hyperpigmented irregular macules on the skin — Pityriasis Versicolor presents as irregular hypo and hyperpigmented macules, predominantly on the trunk, chest, and upper arms, caused by Malassezia furfur .

Question 17

A 2-year-old girl develops a rash with raised borders on her face and arms. The source of infection is found to be the pet cat, which has the same type of rash on its skin. Which fungi is the most likely common cause?

Accepted Answer

Microsporum canis — Microsporum canis is a zoophilic dermatophyte commonly transmitted from cats and dogs to humans, causing tinea corporis (ringworm).

Question 18

Which of the following is the most correct statement regarding Deuteromycetes, also known as Fungi Imperfecti?

Accepted Answer

The sexual reproduction method is not clearly known — Deuteromycetes are characterized by the absence or unknown nature of their sexual (perfect) reproductive stage. They reproduce asexually via conidia.

Question 19

Which of the following statements about fungi is NOT true?

Accepted Answer

Some fungi are photosynthetic — Fungi are strictly heterotrophic and cannot photosynthesize; they obtain nutrients by absorption.

Question 20

Most dimorphic pathogens exist in which forms at which temperatures?

Accepted Answer

Filamentous at 23°C and yeast forms at 37°C — Dimorphic fungi typically grow as filamentous molds at environmental temperatures (around 23-25°C) and as yeast forms at human body temperature (37°C).

Question 21

A fungal mycelium may contain which of the following?

Accepted Answer

All of the above — A fungal mycelium can exhibit septate or coenocytic hyphae, always has chitin in its cell walls, and being eukaryotic, contains mitochondria.

Question 22

All of the following are examples of asexual spore formation EXCEPT:

Accepted Answer

Basidiospores — Basidiospores are sexual spores, produced through meiosis in Basidiomycota. Arthrospores, conidia, and sporangiospores are all forms of asexual reproduction. Yeast reproduction is typically asexual budding.

Question 23

Which of the following is a correct statement about the mechanisms of action of antifungal drugs?

Accepted Answer

Azoles inhibit ergosterol synthesis. — Azoles inhibit the enzyme lanosterol 14-α-demethylase, a key step in ergosterol biosynthesis. Polyenes bind ergosterol. Allylamines also inhibit ergosterol synthesis. Echinocandins inhibit glucan synthesis.

Question 24

A physician visiting a rural Latin American village finds that many mature males but few immature males or females of any age are afflicted by a particular fungal disease. What is the likely diagnosis?

Accepted Answer

Paracoccidioidomycosis — Paracoccidioidomycosis has a striking male predominance, thought to be due to estrogen's protective effect, and is endemic to Latin America.

Question 25

Which fungus has the ability to attack and invade hair?

Accepted Answer

Trichophyton — Both Trichophyton and Microsporum can invade hair. Epidermophyton infects only skin and nails. Rhizopus and Sporothrix are not dermatophytes.

Question 26

A farmer in Mississippi presents with a chronic cough. Chest X-ray reveals an opaque mass. Biopsy of the lung shows macrophages with multiple yeast forms inside. Which diagnosis is most likely?

Accepted Answer

Histoplasmosis — This is classic for Histoplasmosis: endemic region (Mississippi), farmer, intracellular yeasts within macrophages.

Question 27

Which statement regarding fungal cell walls is correct?

Accepted Answer

Ligands associated with the cell walls of certain fungi mediate attachment to host cells — Fungal cell wall ligands, like mannoproteins, are crucial for adhesion to host cells. Polyenes and azoles target the membrane; echinocandins target cell wall glucans.

Question 28

A 54-year-old man develops worsening headache and progressive weakness in his right arm. Brain scan shows a left cerebral lesion. Surgery reveals an abscess with granulomatous material and darkly pigmented septate hyphae — indicating phaeohyphomycosis. Which genus is most likely responsible?

Accepted Answer

Cladophialophora — Phaeohyphomycosis is caused by melanized fungi with dark hyphae. Cladophialophora bantiana is the most common cause of cerebral phaeohyphomycosis.

Question 29

A 35-year-old West African farmer develops a persistent scaly papule on his leg. Ten months later, wart-like purplish lesions appear, slowly progressing to a cauliflower-like appearance. Chromoblastomycosis is diagnosed. Which statement about this disease is most correct?

Accepted Answer

In tissue, organisms convert to spherical cells that reproduce by fission and exhibit transverse septations — Chromoblastomycosis is characterized by sclerotic bodies (Medlar bodies) in tissue, which are thick-walled, brown spherical cells dividing by fission with transverse septations.

Question 30

An 8-year-old boy has a circular, dry, scaly, and pruritic lesion on his leg. Branching, septate, nonpigmented hyphae are observed in a KOH/calcofluor white preparation of a.”— skin scraping from the skin lesion. What is the diagnostic significance?

Accepted Answer

Dermatophytosis — Branching, septate, nonpigmented hyphae in skin scrapings are diagnostic of dermatophytosis (ringworm/tinea). Phaeohyphomycosis would show pigmented hyphae.

Question 31

Which statement regarding the epidemiology of candidiasis is correct?

Accepted Answer

Patients with A — This question is incomplete. However, generally, impaired neutrophil and monocyte function significantly increases the risk of systemic candidiasis.

Question 32

Which of the following is the drug of choice for Sporotrichosis?

Accepted Answer

Itraconazole — Itraconazole is the first-line treatment for lymphocutaneous and cutaneous sporotrichosis. Amphotericin B is reserved for severe systemic or CNS disease.

Question 33

Which antifungal drug class works by targeting glucans in the fungal cell wall?

Accepted Answer

Echinocandins — Echinocandins (e.g., caspofungin, micafungin) inhibit the synthesis of β-1,3-glucan, a key component of the fungal cell wall.

Question 34

Nystatin belongs to which class of antifungal drugs?

Accepted Answer

Polyenes — Nystatin is a polyene antifungal that binds to ergosterol in the fungal cell membrane, causing leakage and cell death.

Question 35

Which antifungal drug does NOT target ergosterol biosynthesis in the fungal membrane?

Accepted Answer

Micafungin — Micafungin is an echinocandin that targets the fungal cell wall (β-glucan synthesis), not ergosterol. The others target ergosterol biosynthesis.

Question 36

Which pathogenic yeast is NOT a common member of normal human flora or microbiota?

Accepted Answer

Cryptococcus neoformans — Cryptococcus neoformans is an environmental organism and not a normal commensal of humans. The other yeasts are common members of the human microbiota.

Question 37

Which fungus is responsible for mycosis of the foot mostly among the Indian subcontinent?

Accepted Answer

Madurella mycetomatis — Madurella mycetomatis is the most common cause of Eumycetoma (Madura foot) in the Indian subcontinent and Africa.

Question 38

Basidiospores are:

Accepted Answer

Single-celled and found in a club-shaped structure (basidium) — Basidiospores are sexual spores characteristic of Basidiomycota, produced on a basidium.

Question 39

A 70-year-old man with leukemia undergoes bone marrow transplant and is receiving cyclosporine and prednisone. Three weeks later he develops fever, cough, and purulent sputum. KOH prep of sputum reveals septate hyphae with parallel walls and low-angle branching. Which organism is most likely?

Accepted Answer

Aspergillus fumigatus — This describes invasive pulmonary aspergillosis in an immunocompromised patient, characterized by septate hyphae with acute-angle branching.

Question 40

Which of the following is NOT thermodymorphic (thermally dimorphic)?

Accepted Answer

Candida albicans — Candida albicans undergoes morphological changes triggered by environmental factors, not primarily by temperature like true thermally dimorphic fungi.

Question 41

Which human fungal species is also found in the lungs of animals and causes pneumonia in immunocompromised patients?

Accepted Answer

Pneumocystis jiroveci — Pneumocystis jiroveci is a latent commensal in human lungs that causes Pneumocystis pneumonia (PCP) in immunocompromised individuals.

Question 42

Which of the following best describes the hyphae in fungi?

Accepted Answer

The cell wall consists of a polysaccharide called chitin — Fungal cell walls are primarily composed of chitin, providing structural support.

Question 43

What is the best pH growth range for fungi in culture media?

Accepted Answer

pH 4–6 — Fungi generally grow optimally in a mildly acidic environment, with a pH range of 4-6, which is why Sabouraud's agar is commonly used.

Question 44

What color does the fungal cell wall appear when stained with Periodic Acid-Schiff (PAS) stain?

Accepted Answer

Red/Magenta — PAS stain colors polysaccharides, including chitin and glucans in fungal cell walls, bright red/magenta.

Question 45

Single-celled spores formed from fragments of hyphae are called:

Accepted Answer

Arthrospores — Arthrospores are formed by the fragmentation of hyphae into individual cells.

Question 46

Which of the following is a major virulence factor for the fungal pathogen Cryptococcus?

Accepted Answer

Capsule — The polysaccharide capsule of Cryptococcus neoformans is a major virulence factor, inhibiting phagocytosis and immune responses.

Question 47

Which of the following is responsible for causing mycosis of the foot and is also associated with mycetoma in the Indian subcontinent?

Accepted Answer

Madurella spp — Madurella mycetomatis is a primary cause of Eumycetoma (fungal mycetoma) of the foot in the Indian subcontinent. Nocardia causes actinomycetoma.

MYCOLOGY MCQs — Complete Bank

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