Mycology Practice Questions

Q: Denture sore mouth is caused by which of the following microorganisms?

Candida albicans. **Explanation:** **Denture Sore Mouth**, also known as **Chronic Atrophic Candidiasis**, is a common form of oral candidiasis. It is primarily caused by an overgrowth of **Candida albicans** (Option B). The condition typically occurs under ill-fitting or poorly cleaned dentures. The space between the denture base and the palatal mucosa creates a warm, moist, and anaerobic environment with low pH, which promotes the proliferation of Candida. Clinically, it presents as diffuse erythema and edema of the mucosa covered by the denture, often without the typical white "curd-like" patches seen in pseudomembranous candidiasis. **Analysis of Incorrect Options:** * **Option A (Actinomyces):** These are Gram-positive anaerobic bacteria responsible for Actinomycosis ("Lumpy Jaw"). They cause chronic granulomatous lesions with sulfur granules, not generalized mucosal soreness under dentures. * **Option C (Blastomyces):** This is a systemic fungal infection (Blastomycosis) that primarily affects the lungs. While it can have oral manifestations, they usually present as chronic non-healing ulcers or verrucous lesions, not as denture-related stomatitis. **Clinical Pearls for NEET-PG:** * **Newton’s Classification:** Used to grade Denture Stomatitis (Type I: Localized inflammation; Type II: Diffuse erythema; Type III: Papillary hyperplasia). * **Predisposing Factors:** Poor oral hygiene, continuous denture wear (not removing them at night), and xerostomia. * **Management:** Improving denture hygiene, soaking dentures in antifungal solutions (e.g., Nystatin), and ensuring a proper fit. * **Key Association:** Often associated with **Angular Cheilitis** (Perleche), which is also frequently caused by *C. albicans*.

Q: The granules discharged in mycetoma contain which of the following?

Fungal colonies. **Explanation:** The hallmark of **Mycetoma** (Madura foot) is the triad of localized swelling, multiple interconnecting sinus tracts, and the discharge of **granules**. These granules are not merely debris; they are organized, compact **micro-colonies of the causative agent** (either fungi in eumycetoma or filamentous bacteria in actinomycetoma) embedded in a matrix. * **Why Option B is correct:** In eumycetoma, the granules represent dense aggregates of fungal hyphae. The color, size, and consistency of these granules provide a diagnostic clue to the specific species (e.g., black granules in *Madurella mycetomatis*). * **Why Options C and D are incorrect:** While pus cells (neutrophils) and inflammatory cells (lymphocytes, plasma cells, and giant cells) are present in the surrounding tissue and the discharge as part of the host's immune response, they do not constitute the "granule" itself. The granule is the pathogen's structural form within the lesion. * **Why Option A is incorrect:** Although chronic mycetoma can lead to underlying bone destruction (osteomyelitis) with a "moth-eaten" appearance on X-ray, bone spicules are not typically discharged in the sinus fluid. **High-Yield Clinical Pearls for NEET-PG:** 1. **Eumycetoma:** Caused by fungi; granules are usually large and can be black or white. 2. **Actinomycetoma:** Caused by aerobic actinomycetes (e.g., *Nocardia*, *Actinomadura*); granules are usually smaller and white, yellow, or red. 3. **Diagnosis:** Direct microscopy of the granule (KOH mount) reveals the morphology of the agent. 4. **GMS/PAS Stains:** Best for visualizing fungal hyphae within the granules.

Q: All of the following are true about mucormycosis, except:

Long-term deferoxamine therapy. **Explanation:** Mucormycosis is a life-threatening opportunistic infection caused by fungi of the order Mucorales (e.g., *Rhizopus*, *Mucor*). **Why Option D is the correct answer (The "Except"):** Mucorales are characterized by **broad, ribbon-like, aseptate (or sparsely septate)** hyphae that branch at **right angles (90°)**. In contrast, septate hyphae with acute-angle branching (45°) are characteristic of *Aspergillus*. **Analysis of other options:** * **Angioinvasion (Option B):** This is a hallmark of Mucormycosis. The fungi invade blood vessel walls, leading to thrombosis, tissue ischemia, and the characteristic black necrotic eschar. * **Long-term Deferoxamine Therapy (Option C):** This is a known risk factor. *Rhizopus* uses deferoxamine as a **siderophore** to scavenge iron for its growth. (Note: Newer iron chelators like Deferasirox do not increase this risk). * **Lymphatic Invasion (Option A):** While angioinvasion is more prominent, the fungus can spread via lymphatics and direct tissue extension. **NEET-PG High-Yield Pearls:** 1. **Risk Factors:** Uncontrolled Diabetes Mellitus (especially **Ketoacidosis** due to increased free iron), neutropenia, and corticosteroid use. 2. **Diagnosis:** KOH mount or biopsy showing broad, non-septate hyphae. 3. **Clinical Form:** Rhinocerebral mucormycosis is the most common presentation. 4. **Treatment:** Surgical debridement + **Liposomal Amphotericin B** (Drug of choice). Isavuconazole and Posaconazole are alternatives.

Q: A 50-year-old farmer presents with a warty lesion over the left foot. Examination shows warts, cut nodules, and cauliflower-like proliferations. KOH mount shows yeast with dark brown irregular septae. Culture on Sabouraud's agar shows sclerotic bodies. What is the probable diagnosis?

Chromoblastomycosis. ### Explanation **1. Why Chromoblastomycosis is correct:** The clinical presentation and laboratory findings are pathognomonic for **Chromoblastomycosis**, a chronic fungal infection of the subcutaneous tissue. * **Clinical Clues:** It typically affects farmers (trauma-related inoculation) and presents as slow-growing, **warty (verrucous)**, or **cauliflower-like** lesions, usually on the lower limbs. * **Microscopic Clues:** The presence of **Sclerotic bodies** (also known as Medlar bodies, "copper pennies," or Muriform bodies) is the gold standard for diagnosis. These are thick-walled, dark brown, multiseptate fungal cells that divide by binary fission rather than budding. They are produced by dematiaceous (pigmented) fungi like *Fonsecaea pedrosoi* and *Phialophora verrucosa*. **2. Why other options are incorrect:** * **Rhinosporidiosis:** Caused by *Rhinosporidium seeberi*, it typically presents as friable, leafy vascular polyps in the nose or nasopharynx. Histology shows large **sporangia** containing thousands of endospores. * **Mycetoma:** Characterized by a triad of tumefaction (swelling), draining sinuses, and the presence of **grains** (sulfur granules). It does not show sclerotic bodies. * **Entomophthoromycosis:** A subcutaneous zygomycosis presenting as firm, painless, non-pitting edema (usually facial or limb). Histology shows thin-walled hyphae surrounded by an eosinophilic Splendore-Hoeppli phenomenon. **3. High-Yield Clinical Pearls for NEET-PG:** * **Sclerotic Bodies:** Pathognomonic for Chromoblastomycosis; they represent a diagnostic "copper penny" appearance. * **Dematiaceous Fungi:** These fungi produce melanin in their cell walls, giving them a natural brown/black color. * **Treatment:** It is notoriously difficult to treat; **Itraconazole** and Terbinafine are the drugs of choice, often combined with surgery or cryotherapy.

Q: Asteroid bodies are seen in which of the following conditions?

Sporotrichosis. **Explanation:** **Sporotrichosis** is the correct answer. Asteroid bodies (specifically the **Splendore-Hoeppli phenomenon**) are a characteristic histopathological feature of Sporotrichosis, caused by the dimorphic fungus *Sporothrix schenckii*. These bodies consist of a central fungal yeast cell surrounded by a radiating, eosinophilic "star-like" halo of antigen-antibody complexes and host proteins. While not pathognomonic (as they can rarely appear in other granulomatous conditions), they are a classic high-yield association for *Sporothrix* in medical exams. **Analysis of Incorrect Options:** * **A. Cryptococcosis:** Characterized by thick **polysaccharide capsules** visualized with India Ink. Histopathology typically shows "soap bubble" lesions in the brain. * **B. Histoplasmosis:** Characterized by small, intracellular yeast cells found within **macrophages**. It does not typically form asteroid bodies. * **C. Aspergillosis:** Characterized by **septate hyphae with acute-angle (45°) branching**. In allergic forms (ABPA), Curschmann’s spirals or Charcot-Leyden crystals may be seen, but not asteroid bodies. **High-Yield Clinical Pearls for NEET-PG:** * **Sporotrichosis** is often called **"Rose Gardener’s Disease"** due to traumatic inoculation from thorns or sphagnum moss. * **Clinical Presentation:** Presents as a linear chain of nodules along lymphatic drainage (nodular lymphangitis). * **Morphology:** At 25°C (Mold), it shows a **"Flower-like" or "Daisy petal"** arrangement of conidia. At 37°C (Yeast), it shows **"Cigar-shaped"** bodies. * **Treatment:** Drug of choice is **Itraconazole**. Historically, saturated solution of potassium iodide (SSKI) was used.

Q: Desert rheumatism is caused by which of the following fungi?

Coccidioides. **Explanation:** **Coccidioidomycosis**, caused by the dimorphic fungus *Coccidioides immitis* or *C. posadasii*, is endemic to the arid regions of the Southwestern United States (San Joaquin Valley) and Mexico. The term **"Desert Rheumatism"** refers to a specific clinical triad seen in the primary pulmonary form of the disease, consisting of **fever, joint pains (arthralgia), and erythema nodosum.** It is also known as "Valley Fever." **Why other options are incorrect:** * **Paracoccidioides:** Causes South American Blastomycosis. It is characterized by the "pilot’s wheel" appearance on microscopy and typically presents with painful oral mucosal ulcers and lymphadenopathy. * **Blastomyces:** Causes North American Blastomycosis. It is associated with "Broad-Based Budding" yeast and primarily affects the lungs, skin, and bones, but does not present as the "Desert Rheumatism" complex. * **Histoplasma:** Causes "Darling’s Disease" or Spelunker’s lung. It is associated with bird or bat droppings and is characterized by intracellular yeasts within macrophages. **High-Yield Clinical Pearls for NEET-PG:** * **Morphology:** *Coccidioides* is unique among dimorphic fungi because it forms **spherules filled with endospores** in tissue (at 37°C) rather than yeast cells. * **Infective form:** Arthroconidia (found in soil/culture). * **Diagnosis:** Spherules are visualized using KOH or silver stains. * **Erythema Nodosum:** In the context of Coccidioidomycosis, the development of erythema nodosum is actually a **good prognostic sign**, indicating a strong cell-mediated immune response.

Q: A 54-year-old farmer presents with a chronic cough. A chest X-ray reveals a mass lesion with hilar lymphadenopathy. Biopsy of the mass demonstrates multiple, tiny yeast forms within macrophages. What is the most likely diagnosis?

Histoplasmosis. **Explanation:** The clinical presentation and histopathology point directly to **Histoplasmosis**, caused by the dimorphic fungus *Histoplasma capsulatum*. **Why Histoplasmosis is correct:** The hallmark of *Histoplasma* infection is the presence of **small, oval yeast cells (2–4 µm) found within macrophages** (intracellular). In the lungs, these yeasts are phagocytosed by alveolar macrophages but survive and multiply within them. The clinical scenario of a farmer (exposure to soil enriched with bird or bat droppings) presenting with a chronic cough and a mass lesion mimicking bronchogenic carcinoma (the "pseudotumor" presentation) is a classic NEET-PG favorite. **Why other options are incorrect:** * **Blastomycosis:** Characterized by large, **broad-based budding yeasts** with thick, doubly refractile walls. They are typically extracellular and much larger than *Histoplasma*. * **Coccidioidomycosis:** Identified by large **spherules (20–100 µm) filled with endospores**. It is not seen as tiny yeasts within macrophages. * **Paracoccidioidomycosis:** Characterized by large yeasts with multiple buds, resembling a **"Pilot’s wheel"** or "Mickey Mouse" appearance. **High-Yield Clinical Pearls for NEET-PG:** * **Habitat:** Soil contaminated with bird (starlings) or bat droppings (caving/spelunking). * **Stains:** Best visualized with **Gomori Methenamine Silver (GMS)** or PAS stain. * **Key Feature:** It is the only systemic mycosis that is an **obligate intracellular** pathogen of the reticuloendothelial system. * **Differential:** Often mimics Tuberculosis (hilar lymphadenopathy, granulomas) or Sarcoidosis.

Q: Which of the following is NOT true regarding cryptococcal infection?

Anticapsular antibody is protective.. **Explanation:** **Cryptococcus neoformans** is an encapsulated yeast that primarily causes meningitis in humans. Understanding its pathogenesis and diagnostic markers is crucial for NEET-PG. **Why Option C is the correct answer (The "False" statement):** While *Cryptococcus* possesses a prominent polysaccharide capsule (Glucuronoxylomannan), the **anticapsular antibodies are NOT protective**. Immunity against Cryptococcus is primarily **cell-mediated (T-cell driven)**. In fact, high titers of capsular antigen in the blood or CSF actually suppress the immune response rather than stimulating a protective one. This is why the infection is so prevalent in patients with impaired T-cell immunity (e.g., HIV/AIDS). **Analysis of Incorrect Options (True statements):** * **Option A:** It is a classic **opportunistic infection**. It occurs predominantly in immunodeficient states, especially in patients with CD4 counts 90%. * **Option D:** *Cryptococcus* species are characteristically **Urease positive**. This biochemical property helps differentiate them from other yeasts like *Candida albicans* (which is urease negative). **High-Yield Clinical Pearls for NEET-PG:** * **Morphology:** Round, budding yeast with a wide halo on **India Ink** preparation (negative staining). * **Culture:** Grows on Sabouraud Dextrose Agar (SDA) as mucoid, cream-colored colonies. On **Niger Seed/Bird Seed Agar**, it produces brownish-black colonies due to **phenoloxidase** activity (melanin production). * **Pathology:** Causes "Soap bubble appearance" lesions in the brain parenchyma. * **Treatment:** Induction with Amphotericin B + Flucytosine, followed by maintenance with Fluconazole.

Q: Which of the following Aspergillus species produces black-colored colonies on Sabouraud's dextrose agar?

A. niger. **Explanation:** The correct answer is **B. A. niger**. **Aspergillus niger** is characterized by its rapid growth on Sabouraud’s Dextrose Agar (SDA), initially appearing white but quickly turning into a dense, **carbon-black** color. This pigmentation is due to the production of dark conidia (spores) on the surface of the colony. Microscopically, it features large, globose, black conidial heads with "biseriate" sterigmata covering the entire vesicle. **Analysis of Incorrect Options:** * **A. fumigatus:** This is the most common pathogenic species. It produces **smoky-green** or grayish-green colonies. It is known for its thermotolerance (growing at 45°C) and "uniseriate" phialides. * **C. A. flavus:** This species typically produces **yellowish-green** or lime-green colonies. It is clinically significant for producing **Aflatoxins**, which are linked to hepatocellular carcinoma. * **D. None of the above:** Incorrect, as A. niger is the classic "black mold." **High-Yield Clinical Pearls for NEET-PG:** 1. **Otomycosis:** *A. niger* is the most common cause of fungal otitis externa, often presenting with a "wet newspaper" appearance or black specks in the ear canal. 2. **Oxalate Crystals:** *A. niger* is unique for producing calcium oxalate crystals in tissue or sputum, which can be a diagnostic clue in biopsies. 3. **Aspergilloma:** While *A. fumigatus* is the primary cause of "fungus balls" in pre-existing lung cavities, all three species mentioned can be involved. 4. **Morphology:** Remember the color mnemonic: **F**umigatus (**F**orest/Green), **Fl**avus (**Fl**uorescent/Yellow-Green), **N**iger (**N**ight/Black).

Q: Broad based budding is seen in which of the following fungal infections?

Blastomycosis. ### Explanation **Blastomycosis (*Blastomyces dermatitidis*)** is the correct answer because it is characterized by a unique morphological feature known as **Broad-Based Budding**. In tissue samples (yeast phase), the daughter cell remains attached to the mother cell by a wide neck, making the base of the bud nearly as wide as the cell itself. The yeast cells are typically large (8–15 µm) with thick, "doubly refractile" walls. #### Analysis of Incorrect Options: * **A. Coccidiomycosis:** Does not exist as yeast in tissue. Instead, it forms large **spherules** (20–100 µm) filled with numerous small **endospores**. * **B. Paracoccidiomycosis:** Characterized by multiple narrow-based buds surrounding a central large yeast cell, resembling a **"Pilot’s Wheel"** or **"Mickey Mouse"** appearance. * **C. Cryptococcosis:** This is a monomorphic yeast characterized by **narrow-based budding** and a prominent polysaccharide capsule (visualized with India Ink). #### NEET-PG High-Yield Pearls: * **Blastomycosis Mnemonic:** "B" for **B**lasto, **B**road-based budding, **B**one involvement (common site of dissemination), and **B**ig (large yeast). * **Geographic distribution:** Primarily found in the Ohio and Mississippi River Valleys (similar to Histoplasmosis). * **Dimorphism:** These fungi are "molds in the cold (25°C) and yeasts in the heat (37°C)." * **Histoplasmosis (Comparison):** Shows small, intracellular yeasts within macrophages (no broad budding).

Question 1

Denture sore mouth is caused by which of the following microorganisms?

Accepted Answer

Candida albicans

Answer

Actinomyces

Answer

Blastomyces

Answer

None of the above

Question 2

The granules discharged in mycetoma contain which of the following?

Accepted Answer

Fungal colonies

Answer

Bone spicules

Answer

Pus cells

Answer

Inflammatory cells

Question 3

All of the following are true about mucormycosis, except:

Accepted Answer

Long-term deferoxamine therapy

Answer

Lymphatic invasion

Answer

Angioinvasion

Answer

Septate hyphae

Question 4

A 50-year-old farmer presents with a warty lesion over the left foot. Examination shows warts, cut nodules, and cauliflower-like proliferations. KOH mount shows yeast with dark brown irregular septae. Culture on Sabouraud's agar shows sclerotic bodies. What is the probable diagnosis?

Accepted Answer

Chromoblastomycosis

Answer

Rhinosporidiosis

Answer

Mycetoma

Answer

Entomophthoromycosis

Question 5

Asteroid bodies are seen in which of the following conditions?

Accepted Answer

Sporotrichosis

Answer

Cryptococcosis

Answer

Histoplasmosis

Answer

Aspergillosis

Question 6

Desert rheumatism is caused by which of the following fungi?

Accepted Answer

Coccidioides

Answer

Paracoccidioides

Answer

Blastomyces

Answer

Histoplasma

Question 7

A 54-year-old farmer presents with a chronic cough. A chest X-ray reveals a mass lesion with hilar lymphadenopathy. Biopsy of the mass demonstrates multiple, tiny yeast forms within macrophages. What is the most likely diagnosis?

Accepted Answer

Histoplasmosis

Answer

Blastomycosis

Answer

Coccidioidomycosis

Answer

Paracoccidioidomycosis

Question 8

Which of the following is NOT true regarding cryptococcal infection?

Accepted Answer

Anticapsular antibody is protective.

Answer

Occurs in immunodeficient states.

Answer

Capsular antigen in CSF is a rapid method of detection.

Answer

Urease positive.

Question 9

Which of the following Aspergillus species produces black-colored colonies on Sabouraud's dextrose agar?

Accepted Answer

A. niger

Answer

A. fumigatus

Answer

A. flavus

Answer

None of the above

Question 10

Broad based budding is seen in which of the following fungal infections?

Accepted Answer

Blastomycosis

Answer

Coccidiomycosis

Answer

Paracoccidiomycosis

Answer

Cryptococcosis

Mycology — MCQs

Mycology — MCQs

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