Mycology Practice Questions

Q: Which of the following is NOT a cause of Madura foot?

Mucor. **Explanation:** **Madura foot (Mycetoma)** is a chronic, granulomatous, subcutaneous infection characterized by a clinical triad of **localized swelling, multiple interconnecting sinus tracts, and the discharge of grains.** It is caused by two distinct groups of organisms: **Eumycetoma** (fungal) and **Actinomycetoma** (filamentous bacteria). **Why Mucor is the correct answer:** **Mucor** is a member of the Zygomycetes family and causes **Mucormycosis**, an acute, aggressive, angioinvasive infection typically seen in immunocompromised patients or those with uncontrolled diabetes. It does not cause chronic granulomatous mycetoma or produce grains. **Analysis of other options:** * **Pseudallescheria boydii:** This is the most common cause of fungal mycetoma (**Eumycetoma**) worldwide. It typically produces white-to-yellow grains. * **Actinomycetes:** This is a broad group of filamentous, Gram-positive bacteria. **Actinomycetoma** accounts for the majority of cases in India (e.g., *Actinomadura madurae*). * **Nocardia:** Species like *Nocardia brasiliensis* are major causes of **Actinomycetoma**. They are partially acid-fast and produce fine, white-to-yellow grains. **High-Yield Clinical Pearls for NEET-PG:** * **The Grains:** The color of the grain can hint at the etiology. Black grains are always fungal (*Madurella mycetomatis*), while red grains are characteristic of *Actinomadura pelletieri*. * **Diagnosis:** The gold standard is the histopathological examination of the grain. * **Radiology:** The **"Dot-in-circle" sign** on MRI is a pathognomonic feature of mycetoma. * **Treatment:** Actinomycetoma responds well to antibiotics (Welsh regimen: Amikacin + Cotrimoxazole), whereas Eumycetoma often requires long-term antifungals (Itraconazole) and surgical debridement.

Q: A 40-year-old man presented with swelling over his foot with multiple sinus discharge. What is the likely diagnosis?

Madura mycosis. ***Madura mycosis*** - **Foot swelling** with **multiple sinus discharge** forms the classic triad of **mycetoma** (Madura foot), caused by fungal (**eumycetoma**) or bacterial (**actinomycetoma**) organisms. - The discharge typically contains **colored granules** (black for **Madurella mycetomatis**, white/yellow for **Nocardia** species) which are pathognomonic for this condition. *Acute myelitis* - Refers to **spinal cord inflammation** causing neurological deficits like **paraplegia** or **quadriplegia**, not foot swelling. - Presents with **motor weakness**, **sensory loss**, and **bladder dysfunction**, none of which match this clinical picture. *Chronic Osteomyelitis* - Typically presents with **single draining sinus** rather than multiple sinuses, and lacks the characteristic **granule discharge**. - More commonly affects **long bones** and is associated with **systemic symptoms** like fever and elevated inflammatory markers. *Dracunculosis* - Caused by **Dracunculus medinensis** (Guinea worm) presenting as a **single blister** with protruding worm, not multiple sinuses. - Endemic to specific regions in **Africa** and involves **contaminated water** consumption, with the worm emerging through skin after one year.

Q: Cigar-shaped yeast cells are seen with which of the following organisms?

S. schenkii. **Explanation:** The correct answer is **B. S. schenkii**. *Sporothrix schenckii* is a **dimorphic fungus**, meaning it exists as a mold in the environment (at 25°C) and as a yeast in human tissue (at 37°C). The characteristic morphological feature of the yeast phase in tissue or culture is the presence of **"cigar-shaped"** (elongated, fusiform) budding cells. This is a classic high-yield microscopic finding used to identify Sporotrichosis, often clinically associated with "Rose gardener’s disease." **Why the other options are incorrect:** * **C. albicans:** Typically presents as oval budding yeast cells with **pseudohyphae** and the ability to form true hyphae (germ tubes). * **H. capsulatum:** Appears as small, oval, **intracellular** yeast cells (often found within macrophages). They are not elongated or cigar-shaped. * **C. neoformans:** Characterized by round-to-oval yeast cells surrounded by a thick, **polysaccharide capsule**, best visualized with India Ink (negative staining). **High-Yield Clinical Pearls for NEET-PG:** 1. **Asteroid Bodies:** In tissue sections, *S. schenckii* may show a central yeast cell surrounded by eosinophilic radiating processes (Splendore-Hoeppli phenomenon). 2. **Clinical Presentation:** Typically presents as a linear chain of nodules following lymphatic drainage (**lymphocutaneous spread**) after traumatic inoculation (e.g., thorn prick). 3. **Drug of Choice:** **Itraconazole** is the preferred treatment. Historically, saturated solution of potassium iodide (SSKI) was used. 4. **Culture:** At 25°C, it produces "flowerette" or **daisy-like** arrangements of conidia.

Q: All of the following are dimorphic fungi EXCEPT:

Curvularia. **Explanation:** The correct answer is **Curvularia**. **1. Why Curvularia is the correct answer:** Dimorphic fungi are characterized by their ability to exist in two morphological forms: a **yeast** (or spherule) form at body temperature (37°C) and a **mold** (filamentous) form at room temperature (25°C). **Curvularia** is not dimorphic; it is a **dematiaceous (pigmented) filamentous fungus** (mold) that remains a mold regardless of temperature. It is a common cause of phaeohyphomycosis, fungal keratitis, and allergic fungal sinusitis. **2. Why the other options are incorrect:** * **Penicillium marneffei (Talaromyces marneffei):** A classic dimorphic fungus endemic to Southeast Asia. It is a significant opportunistic infection in HIV patients, characterized by intracellular yeast cells with a central transverse septum. * **Sporothrix schenckii:** The causative agent of "Rose Gardener’s disease." It is a sub-cutaneous dimorphic fungus. In culture (25°C), it shows "flower-like" conidia; in tissue (37°C), it appears as "cigar-shaped" budding yeasts. * **Blastomyces dermatitidis:** A systemic dimorphic fungus. In its yeast form, it is identified by its characteristic **broad-based budding**. **3. NEET-PG High-Yield Pearls:** * **Mnemonic for Dimorphic Fungi:** *"**B**ody **H**eat **P**robably **C**hanges **S**hape"* (**B**lastomyces, **H**istoplasma, **P**aracoccidioides, **C**occidioides, **S**porothrix/T. marneffei). * **Exception:** *Coccidioides immitis* forms **spherules** (not yeasts) in the body at 37°C. * **Candida albicans** is often called "reverse dimorphic" because it forms germ tubes/hyphae at higher temperatures/serum, though it is technically polymorphic.

Q: A man developed a pustule after being pricked by a thorn in the garden. Laboratory examination of the tissue specimen shows cigar-shaped budding yeasts. What is the most probable causative agent?

Sporothrix. **Explanation:** The clinical presentation and laboratory findings are classic for **Sporotrichosis**, caused by the dimorphic fungus **_Sporothrix schenckii_**. **1. Why the correct answer is right:** * **Mechanism of Injury:** The history of a "thorn prick" while gardening is a high-yield clinical clue for **Rose Gardener’s Disease**. The fungus is commonly found in soil, moss, and decaying vegetation. * **Morphology:** _Sporothrix_ is a **thermally dimorphic fungus**. In the tissue (at 37°C), it exists as yeast. The description of **"cigar-shaped" budding yeasts** is the pathognomonic histological feature for this organism. * **Clinical Progression:** It typically begins as a painless pustule or nodule at the site of inoculation, which may later ulcerate and spread along the draining lymphatics (nodular lymphangitis). **2. Why the incorrect options are wrong:** * **B. Sporotrichosis:** This is the name of the **disease**, not the causative agent. The question asks for the "causative agent," making _Sporothrix_ the more precise answer. * **C. Phialophora:** This is a genus of dematiaceous (pigmented) fungi that causes **Chromoblastomycosis**. Histology would show "copper-colored" sclerotic bodies (Medlar bodies), not cigar-shaped yeasts. * **D. Aspergillus:** This is a monomorphic mold characterized by septate hyphae with **acute-angle (45°) branching**. It does not form yeasts in tissue. **High-Yield Clinical Pearls for NEET-PG:** * **Asteroid Bodies:** In tissue, yeasts may be surrounded by eosinophilic material (Splendore-Hoeppli phenomenon), known as Asteroid bodies. * **Culture:** At 25°C, it grows as a mold with "flowerette" or "daisy-like" arrangements of conidia. * **Treatment:** The drug of choice is **Itraconazole**. Historically, saturated solution of potassium iodide (SSKI) was used.

Q: Which of the following statements about mucormycosis is TRUE?

All of the above.. **Explanation:** Mucormycosis (formerly zygomycosis) is an opportunistic, life-threatening infection caused by fungi of the order Mucorales (e.g., *Rhizopus*, *Mucor*, and *Lichtheimia*). 1. **Predisposing Factors (Option B):** The most significant risk factor is **uncontrolled Diabetes Mellitus**, particularly during **Ketoacidosis (DKA)**. The fungi thrive in acidic environments and utilize free iron (released from transferrin during acidosis) for rapid growth. Other risks include neutropenia, corticosteroid use, and organ transplants. 2. **Common Sites (Option A):** The most frequent clinical presentation is **Rhinocerebral mucormycosis**. The infection typically begins in the **nasal turbinates** or sinuses after inhalation of spores, rapidly spreading to the palate, orbit, and brain due to the fungus's angioinvasive nature. 3. **Epidemiology (Option C):** India has the highest prevalence of mucormycosis globally. This was further highlighted during the COVID-19 pandemic (CAM - COVID-associated mucormycosis), driven by high diabetes prevalence and corticosteroid overuse. **Why "All of the above" is correct:** Since the nose is the primary site of entry, diabetes is the classic metabolic trigger, and the disease is endemic/common in India, all statements are factually accurate. **High-Yield Clinical Pearls for NEET-PG:** * **Hallmark Pathology:** Broad, **aseptate** (or sparsely septate) hyphae with **right-angle (90°) branching**. * **Angioinvasion:** The fungus invades blood vessels, leading to thrombosis and characteristic **black necrotic eschars** (on the palate or nasal bridge). * **Diagnosis:** KOH mount of tissue scrapings shows ribbon-like hyphae. * **Treatment:** Surgical debridement + **Liposomal Amphotericin B** (Drug of choice). Isavuconazole or Posaconazole are alternatives.

Q: Penicillium marneffei is commonly associated with which of the following conditions?

Acquired Immunodeficiency Syndrome (AIDS). **Explanation:** *Penicillium marneffei* (now reclassified as ***Talaromyces marneffei***) is a unique **dimorphic fungus** that serves as a major opportunistic pathogen and a defining illness in patients with **Acquired Immunodeficiency Syndrome (AIDS)**, particularly in Southeast Asia (endemic in Thailand, Vietnam, and Southern China). **1. Why Option B is Correct:** In patients with advanced HIV/AIDS (typically with **CD4 counts <100 cells/μL**), *T. marneffei* causes a systemic infection involving the reticuloendothelial system. It is characterized by fever, weight loss, anemia, and distinctive **umbilicated skin lesions** (resembling *Molluscum contagiosum*). The fungus is intracellular, often seen within macrophages, mimicking *Histoplasma capsulatum*. **2. Why Other Options are Incorrect:** * **A. Tuberculosis:** While TB is the most common opportunistic infection in HIV, *T. marneffei* is a fungal pathogen, not a mycobacterial one. They may co-exist, but the fungus is not "associated" with TB itself. * **C. Diabetes Mellitus:** DM is strongly associated with **Mucormycosis** (Zygomycosis) and *Candida* infections, but not specifically with *T. marneffei*. * **D. Kala-azar:** Caused by *Leishmania donovani*, it presents with similar hepatosplenomegaly, but it is a protozoal disease. **Clinical Pearls for NEET-PG:** * **Dimorphism:** It is the only *Penicillium* species that is thermally dimorphic (Mould at 25°C; Yeast at 37°C). * **Laboratory Hallmark:** On Sabouraud Dextrose Agar (SDA) at 25°C, it produces a characteristic **diffusible red pigment**. * **Microscopy:** Yeast cells divide by **fission** (transverse septum), not budding. * **Treatment:** Intravenous Amphotericin B followed by oral Itraconazole.

Q: Pneumocystis jirovecii causes infection primarily in which species?

Rats. **Explanation:** The nomenclature of *Pneumocystis* species is strictly host-specific. While the genus was once thought to contain a single species (*P. carinii*), molecular analysis has proven that each mammalian host is infected by a distinct, genetically unique species of *Pneumocystis* that cannot cross-infect other species. * **Correct Option (A) Rats:** *Pneumocystis carinii* is the specific species that infects rats. Historically, all *Pneumocystis* organisms were referred to as *P. carinii*. However, current taxonomy restricts the name ***P. carinii*** (and *P. wakefieldiae*) specifically to the species found in **rats**. * **Incorrect Option (C) Humans:** The species that causes human infection (Pneumocystis Pneumonia - PCP) is **_Pneumocystis jirovecii_**. It is a common opportunistic infection in HIV/AIDS patients. * **Incorrect Options (B) & (D):** Mice are infected by *P. murina*, and rabbits are infected by *P. oryctolagi*. **High-Yield Clinical Pearls for NEET-PG:** 1. **Taxonomy Shift:** *Pneumocystis* was previously classified as a protozoan but is now classified as a **fungus** based on nucleic acid analysis (rRNA). 2. **Staining:** The gold standard for diagnosis is identifying cysts in bronchoalveolar lavage (BAL) fluid using **Gomori Methenamine Silver (GMS)** stain (appears as crushed ping-pong balls) or Direct Fluorescent Antibody (DFA) staining. 3. **Treatment:** Despite being a fungus, it does not respond to Ergosterol-inhibitors (like Amphotericin B) because it lacks ergosterol. The drug of choice is **Trimethoprim-Sulfamethoxazole (TMP-SMX)**. 4. **Prophylaxis:** Indicated in HIV patients when the **CD4 count falls below 200 cells/mm³**.

Q: All of the following forms sulphur granules except?

Chromoblastomycosis. **Explanation:** The presence of **sulphur granules** (grains) in tissue is a hallmark of chronic granulomatous infections characterized by the formation of microcolonies of the causative organism surrounded by an eosinophilic Splendore-Hoeppli phenomenon. 1. **Why Chromoblastomycosis is the correct answer:** Chromoblastomycosis is a chronic fungal infection caused by dematiaceous (pigmented) fungi like *Fonsecaea pedrosoi*. It is characterized by the presence of **Medlar bodies** (also known as sclerotic bodies, copper-penny bodies, or muriform bodies) in tissue biopsies. It **does not** produce sulphur granules. 2. **Analysis of Incorrect Options:** * **Actinomycosis:** Classically produces large, yellow, hard "sulphur granules" composed of filamentous *Actinomyces israelii*. These are most commonly seen in cervicofacial infections ("lumpy jaw"). * **Mycetoma:** This clinical syndrome (Madura foot) is defined by a triad of localized swelling, underlying bone involvement, and the discharge of **grains/granules** through sinus tracts. It can be Eumycetoma (fungal) or Actinomycetoma (bacterial). * **Botryomycosis:** Despite the name, this is a chronic **bacterial** infection (most commonly *Staphylococcus aureus*) that mimics a fungal infection by forming granules in the tissue. **High-Yield Clinical Pearls for NEET-PG:** * **Medlar Bodies:** Pathognomonic for Chromoblastomycosis; they are thick-walled, brown, globe-shaped structures that divide by septation (not budding). * **Sulphur Granule Colors:** * *Actinomyces*: Yellow * *Actinomadura madurae*: White/Cream * *Actinomadura pelletieri*: Red * *Madurella mycetomatis*: Black * **Splendore-Hoeppli Phenomenon:** The eosinophilic material surrounding the granules in these conditions represents an antigen-antibody complex.

Question 1

Which of the following is NOT a cause of Madura foot?

Accepted Answer

Mucor

Answer

Pseudallescheria

Answer

Actinomycetes

Answer

Nocardia

Question 2

A 40-year-old man presented with swelling over his foot with multiple sinus discharge. What is the likely diagnosis?

Accepted Answer

Madura mycosis

Answer

Acute myelitis

Answer

Chronic Osteomyelitis

Answer

Dracunculosis

Question 3

Cigar-shaped yeast cells are seen with which of the following organisms?

Accepted Answer

S. schenkii

Answer

C. albicans

Answer

H. capsulatum

Answer

C. neoformans

Question 4

All of the following are dimorphic fungi EXCEPT:

Accepted Answer

Curvularia

Answer

Penicillium marneffei

Answer

Sporothrix schenkii

Answer

Blastomyces dermatitidis

Question 5

Madura foot is caused by?

Accepted Answer

Fungal infection

Answer

Parasites

Answer

Viral infection

Answer

Bacterial infection

Question 6

A man developed a pustule after being pricked by a thorn in the garden. Laboratory examination of the tissue specimen shows cigar-shaped budding yeasts. What is the most probable causative agent?

Accepted Answer

Sporothrix

Answer

Sporotrichosis

Answer

Phialophora

Answer

Aspergillus

Question 7

Which of the following statements about mucormycosis is TRUE?

Accepted Answer

All of the above.

Answer

The nose is a common site for mucormycosis.

Answer

Diabetes mellitus is a predisposing factor for mucormycosis.

Answer

Mucormycosis is common in India.

Question 8

Penicillium marneffei is commonly associated with which of the following conditions?

Accepted Answer

Acquired Immunodeficiency Syndrome (AIDS)

Answer

Tuberculosis

Answer

Diabetes Mellitus

Answer

Kala-azar

Question 9

Pneumocystis jirovecii causes infection primarily in which species?

Accepted Answer

Rats

Answer

Mice

Answer

Humans

Answer

Rabbits

Question 10

All of the following forms sulphur granules except?

Accepted Answer

Chromoblastomycosis

Answer

Botryomycosis

Answer

Mycetoma

Answer

Actinomycosis

Mycology — MCQs

Mycology — MCQs

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