Mycology — MCQs

A preterm, low birth weight infant delivered by LSCS after IVF was put on a ventilator in NICU for severe Respiratory Distress Syndrome. The respiratory distress subsided on day 7 and Total Parenteral Nutrition with lipid formulation was started from day 10. The neonate developed signs of sepsis on day 15. What is the most likely causative agent?

Mycology Indian Medical PG Practice Questions and MCQs

Question 121: Healing with calcification is a characteristic feature of which fungal infection?

A. Cryptococcosis
B. Mucomycosis
C. Aspergillosis
D. Histoplasmosis (Correct Answer)

Explanation: **Explanation:** **Histoplasmosis** (caused by *Histoplasma capsulatum*) is the correct answer because it is a dimorphic fungus that primarily infects the reticuloendothelial system. When inhaled, the spores are engulfed by alveolar macrophages. In immunocompetent individuals, the body mounts a granulomatous inflammatory response similar to Tuberculosis. As these granulomas heal, they frequently undergo **dystrophic calcification**. This results in characteristic "buckshot" calcifications in the lungs, spleen, and liver, which are visible on imaging. **Why other options are incorrect:** * **Cryptococcosis:** Caused by *Cryptococcus neoformans*, it typically presents as meningitis or pulmonary nodules (torulomas) in immunocompromised patients. It does not typically result in calcified granulomas. * **Mucormycosis:** This is an angioinvasive infection characterized by extensive tissue necrosis and infarction. It is an acute, fulminant disease (especially in diabetics) and does not follow a chronic granulomatous healing pattern with calcification. * **Aspergillosis:** While it can cause various pulmonary syndromes (Aspergilloma, ABPA, Invasive Aspergillosis), it is characterized by septate hyphae with acute-angle branching. Healing via calcification is not a hallmark feature. **High-Yield Clinical Pearls for NEET-PG:** * **The "Great Mimicker":** Histoplasmosis clinically and radiologically mimics Tuberculosis. * **Morphology:** It is an **intracellular** fungus (found inside macrophages) and is NOT encapsulated (despite the name *capsulatum*). * **Source:** Associated with **bird or bat droppings** (guano); common in explorers of caves (Speleologist’s lung). * **Diagnosis:** Culture on Sabouraud Dextrose Agar (SDA) shows tuberculate macroconidia.

Question 122: Mycetoma foot can be caused by which of the following organisms?

A. Cladosporium
B. Phialophora jeanselmei
C. Madurella mycetoma
D. Allescheria boydii (Correct Answer)

Explanation: **Explanation:** **Mycetoma** (Madura foot) is a chronic, granulomatous infection of the subcutaneous tissue, characterized by a clinical triad of **localized swelling, multiple interconnecting sinuses, and the discharge of grains.** It is broadly classified into two types: 1. **Actinomycetoma:** Caused by filamentous bacteria (e.g., *Nocardia, Actinomadura*). 2. **Eumycetoma:** Caused by true fungi. **Why Option D is Correct:** **_Allescheria boydii_** (also known as *Pseudallescheria boydii* or its asexual form *Scedosporium apiospermum*) is a leading cause of **Eumycetoma**, particularly in temperate regions. It typically produces **white/pale grains** in the sinus discharge. **Analysis of Incorrect Options:** * **A & B (Cladosporium & Phialophora):** These are dematiaceous (pigmented) fungi primarily associated with **Chromoblastomycosis**, not mycetoma. Chromoblastomycosis is characterized by verrucous (wart-like) skin lesions and the presence of **Sclerotic bodies** (Medlar bodies/copper-penny bodies) on histology, rather than grains and sinuses. * **C (Madurella mycetoma):** While *Madurella mycetomatis* is the most common cause of fungal mycetoma worldwide (producing **black grains**), the question specifically asks which of the following *can* cause it. In the context of this specific MCQ set, *Allescheria boydii* is the designated correct answer, often highlighted in exams to test knowledge of white-grain eumycetoma. **NEET-PG High-Yield Pearls:** * **Grains:** The color of the grain is a diagnostic clue. *Madurella* = Black; *Actinomadura madurae* = Creamy/White; *Actinomadura pelletieri* = Red. * **Diagnosis:** The gold standard is the demonstration of grains in the discharge or biopsy. * **Treatment:** Eumycetoma (Fungal) requires long-term antifungals (e.g., Itraconazole) and often surgery, whereas Actinomycetoma (Bacterial) responds well to the **Welsh Regimen** (Amikacin + Cotrimoxazole).

Question 123: Which of the following is NOT true regarding sporotrichosis?

A. Caused by Sporothrix schenkii
B. Spread along lymphatics
C. Medullar bodies are seen (Correct Answer)
D. Potassium iodide is the drug of choice

Explanation: **Explanation:** Sporotrichosis, often called **"Rose Gardener’s Disease,"** is a chronic granulomatous infection caused by the dimorphic fungus *Sporothrix schenckii*. **Why Option C is the correct answer (The False Statement):** **Medullar bodies** (also known as sclerotic bodies, copper-penny bodies, or Medlar bodies) are the hallmark histopathological finding of **Chromoblastomycosis**, not sporotrichosis. In sporotrichosis, the characteristic histological findings are **Asteroid bodies** (an eosinophilic Splendore-Hoeppli material surrounding a central yeast cell) and cigar-shaped yeast cells. **Analysis of other options:** * **Option A:** It is indeed caused by *Sporothrix schenckii*, a thermally dimorphic fungus (mold in nature/25°C, yeast in tissue/37°C). * **Option B:** The most common clinical presentation is **lymphocutaneous sporotrichosis**, where a primary nodule at the site of inoculation (usually a thorn prick) ulcerates and spreads linearly along the draining **lymphatic channels**. * **Option D:** Historically, **Saturated Solution of Potassium Iodide (SSKI)** was the drug of choice. While Itraconazole is now the modern gold standard for cutaneous cases, SSKI remains a classic, effective, and frequently tested treatment option in exams. **High-Yield Clinical Pearls for NEET-PG:** * **Source:** Traumatic inoculation from soil, rose thorns, or sphagnum moss. * **Morphology:** "Cigar-shaped" yeast cells in tissue. * **Asteroid Bodies:** Represent an antigen-antibody complex (Splendore-Hoeppli phenomenon). * **Treatment:** Itraconazole (Current DOC); SSKI (Classic DOC); Amphotericin B (for systemic/disseminated disease).

Question 124: Cryptococcus neoformans is a type of organism. What classification best describes it?

A. Protozoa
B. Fungus (Correct Answer)
C. Parasite
D. Mycoplasma

Explanation: ### Explanation **Correct Answer: B. Fungus** *Cryptococcus neoformans* is a medically important **encapsulated yeast** (a type of fungus). It is classified under the phylum Basidiomycota. The hallmark of this organism is its thick **polysaccharide capsule** (composed primarily of glucuronoxylomannan), which serves as its major virulence factor by inhibiting phagocytosis. It is typically found in soil contaminated with **pigeon droppings** and is acquired via inhalation. **Why other options are incorrect:** * **A. Protozoa:** Protozoa are single-celled eukaryotic organisms (like *Plasmodium* or *Amoeba*) that lack a cell wall. *Cryptococcus* has a rigid fungal cell wall containing chitin and glucans. * **C. Parasite:** While "parasite" is a broad term, in medical microbiology, it specifically refers to protozoa and helminths. Fungi are classified separately. * **D. Mycoplasma:** These are the smallest free-living bacteria. They are unique because they **lack a cell wall** entirely, whereas *Cryptococcus* has a complex cell wall and a capsule. **High-Yield Clinical Pearls for NEET-PG:** * **Morphology:** It is a **monomorphic yeast** (not dimorphic). It shows narrow-based budding. * **Staining:** The capsule is best visualized using **India Ink** (negative staining), appearing as a clear halo against a dark background. * **Histopathology:** **Mucicarmine stain** specifically stains the capsule bright red. * **Clinical Presentation:** It is the most common cause of fungal meningitis in immunocompromised patients (especially those with HIV/AIDS). * **Biochemical Test:** It is **Urease positive** and produces melanin on Niger seed (Birdseed) agar.

Question 125: Which of the following is FALSE regarding Phaeohyphomycosis?

A. It can produce brain abscess.
B. It exists in hyphal form.
C. It produces sclerotic bodies. (Correct Answer)
D. It is caused by dematiaceous fungi, other than fungi causing chromoblastomycosis.

Explanation: **Explanation:** Phaeohyphomycosis is a clinical syndrome caused by **dematiaceous (pigmented/melanized) fungi** that exist in tissue as **pigmented hyphae, pseudohyphae, or yeast-like cells**, but notably **not** as sclerotic bodies. **Why Option C is the correct (False) statement:** The hallmark of Phaeohyphomycosis is the presence of dark, branched hyphae in tissue. **Sclerotic bodies** (also known as Medlar bodies, copper pennies, or muriform bodies) are the pathognomonic diagnostic feature of **Chromoblastomycosis**, not Phaeohyphomycosis. This is a critical distinction in medical mycology. **Analysis of other options:** * **Option A:** Phaeohyphomycosis can be systemic. *Cladophialophora bantiana* is a neurotropic dematiaceous fungus known for causing brain abscesses, particularly in immunocompromised patients. * **Option B:** Unlike Chromoblastomycosis, which presents as thick-walled muriform cells, Phaeohyphomycosis characteristically exists in a **hyphal form** (often irregular or beaded) within the host tissue. * **Option C:** This is the definition of the condition. It is a "catch-all" term for infections caused by any dematiaceous fungi that do not meet the specific clinical/histopathological criteria for Chromoblastomycosis or Mycetoma. **High-Yield Clinical Pearls for NEET-PG:** * **Pigmentation:** The dark color is due to **Melanin** in the cell walls, which acts as a virulence factor by protecting the fungus from host immune responses. * **Staining:** While naturally pigmented, **Masson-Fontana stain** (specific for melanin) can be used to confirm the diagnosis. * **Common Organisms:** *Exophiala jeanselmei*, *Wangiella dermatitidis*, and *Cladophialophora bantiana*. * **Key Distinction:** * Sclerotic bodies = Chromoblastomycosis. * Pigmented Hyphae = Phaeohyphomycosis.

Question 126: What is the causative agent of rhinosporidiosis?

A. Bacteria (Correct Answer)
B. Fungus
C. Protozoa
D. Virus

Explanation: **Explanation:** The causative agent of rhinosporidiosis is ***Rhinosporidium seeberi***. Historically, this organism was classified as a fungus due to its morphology (production of sporangia and spores) and its staining characteristics (PAS and GMS positive). However, modern molecular phylogenetic analysis (18S rRNA sequencing) has reclassified it as a **Mesomycetozoean**, a group of aquatic protists situated at the evolutionary boundary between animals and fungi. **Why Option A is marked as correct (Contextual Note):** In many traditional medical curricula and older textbooks, *Rhinosporidium* was grouped under "Fungal-like" organisms. However, strictly speaking, it is neither a bacterium, a true fungus, nor a virus. In the context of this specific question format (where "Bacteria" is marked correct), it is likely a technical error in the source key, as *R. seeberi* is biologically a **protist (Mesomycetozoea)**. If "Protist" or "Parasite" is not an option, it is traditionally studied in **Mycology** sections. **Analysis of Options:** * **B. Fungus:** Incorrect. While it resembles fungi morphologically, it cannot be cultured on fungal media (SDA) and lacks chitin in its cell wall. * **C. Protozoa:** Incorrect. While it is a protist, it belongs to the *Mesomycetozoea* clade, which is distinct from classical protozoa. * **D. Virus:** Incorrect. It is a complex, multicellular eukaryotic organism. **Clinical Pearls for NEET-PG:** * **Habitat:** Found in stagnant water; common in sand dredgers and those bathing in ponds. * **Clinical Presentation:** Characterized by **friable, leafy, strawberry-like polypoid masses** in the nose or nasopharynx. * **Diagnosis:** Histopathology shows large **thick-walled sporangia** (up to 350 µm) containing thousands of **endospores**. * **Treatment:** Surgical excision with wide-base cauterization; **Dapsone** is the medical adjunct of choice.

Question 127: All the following organisms lack a capsule except?

A. Histoplasma capsulatum
B. Cryptococcus neoformans (Correct Answer)
C. Candida albicans
D. Coccidioides immitis

Explanation: **Explanation:** The presence of a polysaccharide capsule is a defining virulence factor for **Cryptococcus neoformans**. In medical mycology, it is a high-yield fact that most pathogenic fungi are non-capsulated; *Cryptococcus* is the notable exception. **1. Why Cryptococcus neoformans is correct:** It is an encapsulated yeast. The capsule is composed of **Glucuronoxylomannan (GXM)**, which inhibits phagocytosis and allows the fungus to evade the host immune system. In clinical practice, this capsule is visualized using **India Ink** (negative staining), where it appears as a clear halo against a dark background. It is also stained by **Mucicarmine** (bright red). **2. Why the other options are incorrect:** * **Histoplasma capsulatum:** Despite its name, it is **not** encapsulated. It was misnamed by Samuel Darling, who mistook the halo seen in tissue sections (a shrinkage artifact) for a capsule. It is an intracellular fungus found within macrophages. * **Candida albicans:** This is a budding yeast that forms pseudohyphae and true hyphae (germ tubes). It lacks a polysaccharide capsule. * **Coccidioides immitis:** This dimorphic fungus exists as **spherules** containing endospores in tissue. While the spherule wall is thick, it is not classified as a capsule. **NEET-PG High-Yield Pearls:** * **Mnemonic for Capsulated Organisms:** "Some Killers Have Nice Capsules" (**S**trep pneumoniae, **K**lebsiella, **H**aemophilus influenzae, **N**eisseria meningitidis, **C**ryptococcus). * **Cryptococcal Antigen (CrAg):** Detected via Latex Agglutination or Lateral Flow Assay; it is more sensitive than India Ink. * **Histoplasma:** Look for "narrow-based budding yeast inside macrophages" in clinical vignettes.

Question 128: Rhinosporidium seeberi is a

A. Fungi
B. Aquatic protist (Correct Answer)
C. Bacteria
D. Virus

Explanation: **Explanation:** **Rhinosporidium seeberi** was traditionally classified as a fungus for over a century due to its morphology (production of sporangia and spores) and its staining characteristics (Gomori Methenamine Silver positive). However, modern molecular analysis (18S rRNA sequencing) has reclassified it as an **aquatic protist** belonging to the class **Mesomycetozoea**, a group of fish parasites located at the evolutionary boundary between animals and fungi. * **Why Option B is correct:** Phylogenetic studies show it is not a true fungus but a protist. It is typically found in stagnant water and soil, and infection is usually acquired through contact with contaminated water (e.g., swimming in ponds). * **Why Option A is incorrect:** While it resembles fungi morphologically (producing thick-walled sporangia containing thousands of endospores), it cannot be cultured on fungal media (like SDA) and does not respond to standard antifungal therapy. * **Why Options C & D are incorrect:** Its complex life cycle, large size (sporangia up to 350 µm), and eukaryotic structure rule out bacteria and viruses. **Clinical Pearls for NEET-PG:** * **Clinical Presentation:** Causes **Rhinosporidiosis**, characterized by friable, leafy, **strawberry-like polypoid masses** in the nose (most common) or conjunctiva. * **Epidemiology:** Highly endemic in **South India** (Tamil Nadu, Kerala) and Sri Lanka. * **Diagnosis:** Histopathology shows large, thick-walled **sporangia** filled with hundreds of **endospores**. * **Treatment:** The treatment of choice is **surgical excision** with wide cautery of the base. Dapsone is sometimes used to prevent recurrence.

Question 129: Which of the following is a fungus?

A. Klebsiella
B. Clostridia
C. Pneumocystis jirovecii (Correct Answer)
D. Listeria

Explanation: **Explanation:** The correct answer is **Pneumocystis jirovecii**. Historically, *Pneumocystis jirovecii* was classified as a protozoan due to its morphological features (cysts and trophozoites) and lack of response to traditional antifungals like Amphotericin B. However, modern DNA analysis and molecular studies have definitively reclassified it as a **unicellular fungus**. It contains fungal-specific enzymes and ribosomal RNA sequences, although its cell membrane contains **cholesterol** instead of the typical fungal ergosterol—a high-yield distinction for exams. **Analysis of Incorrect Options:** * **A. Klebsiella:** A Gram-negative, encapsulated, non-motile bacillus (Bacteria) known for causing "currant jelly sputum" pneumonia. * **B. Clostridia:** A genus of Gram-positive, spore-forming, anaerobic bacilli (Bacteria) responsible for diseases like tetanus, botulism, and gas gangrene. * **D. Listeria:** A Gram-positive, non-spore-forming motile bacillus (Bacteria) often associated with foodborne illness and neonatal meningitis. **NEET-PG High-Yield Pearls:** 1. **Staining:** *P. jirovecii* is best visualized using **Gomori Methenamine Silver (GMS)** stain, appearing as crushed ping-pong ball-shaped cysts. 2. **Clinical Presentation:** It is the most common opportunistic infection in HIV/AIDS patients (CD4 count <200 cells/µL), causing interstitial pneumonia with a "ground-glass" appearance on HRCT. 3. **Treatment:** Unlike other fungi, the drug of choice is **Trimethoprim-Sulfamethoxazole (TMP-SMX)**, not antifungals.

Question 130: A preterm, low birth weight infant delivered by LSCS after IVF was put on a ventilator in NICU for severe Respiratory Distress Syndrome. The respiratory distress subsided on day 7 and Total Parenteral Nutrition with lipid formulation was started from day 10. The neonate developed signs of sepsis on day 15. What is the most likely causative agent?

A. Gram negative bacteria
B. Gram positive bacteria
C. Candida
D. Malassezia (Correct Answer)

Explanation: **Explanation:** The clinical scenario describes a classic presentation of **Malassezia furfur fungemia** (specifically *M. furfur* or *M. pachydermatis*). **Why Malassezia is the correct answer:** *Malassezia furfur* is a lipophilic yeast that is part of the normal skin flora. In the NICU setting, it is a well-known cause of catheter-related bloodstream infections (CRBSI) in neonates receiving **Total Parenteral Nutrition (TPN) with lipid emulsions**. The lipid formulation provides the necessary growth environment for this fungus, which can colonize the indwelling central venous catheter and lead to systemic sepsis. Key risk factors present in this case include prematurity, low birth weight, and prolonged NICU stay with lipid-rich TPN. **Why other options are incorrect:** * **Gram-negative/Gram-positive bacteria:** While these are common causes of early and late-onset neonatal sepsis, the specific mention of **lipid formulations** in the clinical vignette is a "buzzword" designed to point the student toward a lipophilic organism. * **Candida:** *Candida albicans* is the most common cause of fungal sepsis in neonates. However, it does not have a specific requirement for or association with lipid emulsions like *Malassezia* does. **High-Yield Clinical Pearls for NEET-PG:** 1. **Culture Requirement:** *Malassezia furfur* requires **long-chain fatty acids** (e.g., sterile olive oil overlay) on Sabouraud Dextrose Agar (SDA) to grow. 2. **Morphology:** On microscopy, it shows a characteristic **"spaghetti and meatballs"** appearance (hyphae and blastoconidia). 3. **Diagnosis:** If a neonate on TPN develops sepsis and blood cultures are negative on routine media, suspect *Malassezia* and request lipid-enriched media. 4. **Management:** Treatment involves stopping the lipid infusion and removing the central catheter.

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Classification of Fungi

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Superficial Mycoses

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Dermatophytes

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Subcutaneous Mycoses

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Candidiasis

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Aspergillosis

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Cryptococcosis

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Zygomycosis

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Endemic Mycoses

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Opportunistic Fungal Infections

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Antifungal Agents

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Mycology — MCQs

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