Mycology Practice Questions

Q: Draining sinuses are seen in which of the following conditions?

Mycetoma. **Explanation:** **Mycetoma** is a chronic, granulomatous infection of the skin and subcutaneous tissue, most commonly affecting the foot (Madura foot). The classic clinical triad of Mycetoma consists of: 1. **Localized swelling** (Tumefaction) 2. **Multiple interconnecting draining sinuses** 3. **Presence of grains** (sulfur-like granules) in the discharge. It is caused by either fungi (**Eumycetoma**) or filamentous bacteria (**Actinomycetoma**). The sinuses serve as channels for the body to discharge these colonial grains. **Analysis of Incorrect Options:** * **Scrofula:** This is tuberculous cervical lymphadenitis. While it can lead to "cold abscesses" that may eventually rupture to form sinuses, it is primarily a lymph node pathology rather than a primary subcutaneous infection characterized by the classic draining sinus triad. * **Lupus Vulgaris:** A progressive form of cutaneous tuberculosis characterized by "apple-jelly nodules" on diascopy. It typically presents as plaques or ulcers rather than deep draining sinuses. * **Pediculosis:** This refers to infestation with lice (head, body, or pubic). It presents with pruritus and excoriations, not deep tissue destruction or sinus formation. **High-Yield Clinical Pearls for NEET-PG:** * **Eumycetoma:** Most common cause worldwide is *Madurella mycetomatis*. Grains are usually black or white. * **Actinomycetoma:** Most common cause in India is *Nocardia brasiliensis* or *Actinomadura madurae*. Grains are usually white, yellow, or red. * **Diagnosis:** Crushing the grains and performing Gram stain/KOH mount is the initial step. * **Dot-in-a-circle sign:** A characteristic MRI finding in Mycetoma where the "dot" represents the grain and the "circle" represents the inflammatory granuloma.

Q: A patient with a previous history of tuberculosis complains of hemoptysis. Chest x-ray reveals an upper lobe mass with a cavity and a crescent-shaped air-fluid level. What is the most likely etiologic agent?

Aspergillus flavus. ### Explanation **Correct Answer: A. Aspergillus flavus** The clinical presentation describes a classic **Aspergilloma** (fungus ball). This occurs when *Aspergillus* species (most commonly *A. fumigatus*, but also *A. flavus*) colonize a pre-existing pulmonary cavity, typically left behind by **Tuberculosis**, sarcoidosis, or bronchiectasis [1]. The pathognomonic radiological sign described is the **Monod sign** (a crescent-shaped air space surrounding a mobile mass within a cavity) [1]. Hemoptysis is the most common clinical symptom due to the erosion of bronchial vessels by the fungus or its metabolic products [3]. **Why the other options are incorrect:** * **B. Coccidioides immitis:** While it can cause thin-walled cavities (coccidioidomycosis), it typically presents with "Valley Fever" symptoms (fever, arthralgia, erythema nodosum) and does not characteristically form a mobile intracavitary fungus ball with a crescent sign. * **C & D. Herpes Simplex Virus (HSV-1 & 2):** These are viral pathogens. HSV-1 can cause necrotizing pneumonia in immunocompromised patients, but it does not present as a chronic intracavitary mass or "fungus ball." **NEET-PG High-Yield Pearls:** * **Air-Crescent Sign:** Also seen in the recovery phase of **Invasive Pulmonary Aspergillosis** (IPA) as necrotic lung tissue separates from healthy parenchyma; however, in a stable patient with a history of TB, it signifies an Aspergilloma [2]. * **Diagnosis:** Sputum culture is often negative; diagnosis is confirmed via **Aspergillus IgG antibodies (precipitins)** and imaging. * **Treatment:** Aspergillomas are relatively resistant to systemic antifungals. **Surgical resection** is the treatment of choice for symptomatic patients (massive hemoptysis). Bronchial Artery Embolization (BAE) is used for acute management of life-threatening bleeding.

Q: In an AIDS patient presenting with fever and cough, a diagnosis of Pneumocystis jirovecii pneumonia is best established by?

Bronchoalveolar lavage. **Explanation:** *Pneumocystis jirovecii* is an opportunistic fungus that primarily colonizes the alveolar spaces. In AIDS patients, it causes severe interstitial pneumonia (PCP). **Why Bronchoalveolar Lavage (BAL) is the correct answer:** BAL is considered the **gold standard diagnostic procedure** for PCP because it provides the highest diagnostic yield (90–95%). Since the organism resides deep within the alveoli, washing the alveolar spaces allows for the collection of a high concentration of trophozoites and cysts, which can then be identified via microscopy. **Analysis of Incorrect Options:** * **A. Transtracheal biopsy:** While highly sensitive, it is an invasive procedure with a high risk of complications like pneumothorax and hemorrhage. It is reserved only when non-invasive methods fail. * **C. Staining for Pneumocystis cysts:** This is a **method of identification**, not a method of specimen collection. While silver stains (Gomori Methenamine Silver) are used to visualize the organism, the question asks how the diagnosis is *best established* (implying the procedure/specimen). * **D. Sputum aspiration and culture:** *P. jirovecii* **cannot be cultured** on routine laboratory media. Furthermore, spontaneous sputum has a very low yield; induced sputum (using hypertonic saline) is preferred as an initial non-invasive step, but BAL remains superior. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** Trimethoprim-Sulfamethoxazole (Cotrimoxazole). * **Radiology:** Characterized by bilateral "ground-glass opacities" or perihilar infiltrates. * **Microscopy:** Look for "crushed ping-pong ball" appearance of cysts on GMS stain or "cup-shaped" organisms. * **Serum Marker:** Elevated **(1,3)-beta-D-glucan** levels are highly suggestive of PCP in the right clinical context.

Q: Barrel-shaped spores are seen with which of the following fungi?

Coccidioides. **Explanation:** The correct answer is **Coccidioides** (Option C). **Why Coccidioides is correct:** *Coccidioides immitis* and *C. posadasii* are dimorphic fungi characterized by a unique life cycle. In the environment (soil) and in laboratory cultures (at 25°C), they form septate hyphae that fragment into highly infectious, thick-walled, **barrel-shaped arthroconidia** (arthrospores). These spores are typically separated by empty "disjunctor cells," giving them a characteristic "beaded" or "barrel" appearance under the microscope. In the human body (37°C), these spores transform into large **spherules** filled with endospores. **Why other options are incorrect:** * **Blastomyces:** Characterized by large, round-to-oval yeast cells with a **broad-based bud** and a thick, "doubly refractile" cell wall. * **Histoplasma:** Typically seen as small, intracellular yeast cells within macrophages. They do not form barrel-shaped spores; their diagnostic feature in culture is the **tuberculate macroconidia** (finger-like projections). * **Candida:** A yeast-like fungus that primarily reproduces by budding (blastoconidia) and forms **pseudohyphae**. In specific conditions (e.g., Cornmeal agar), *C. albicans* forms thick-walled **chlamydospores**. **High-Yield Clinical Pearls for NEET-PG:** * **Coccidioidomycosis** is also known as **Valley Fever** or Desert Rheumatism. * It is the **most virulent** of the systemic mycoses; laboratory cultures are a major biohazard. * **Morphology Shift:** Arthroconidia (Environment/Culture) → Spherules (Tissue). * **Geographic distribution:** Southwestern USA (Arizona, California), Mexico, and Central/South America. * **Clinical Triad:** Fever, joint pain (arthralgia), and erythema nodosum.

Q: A 40-year-old male presents with verrucous skin lesions. Microscopic examination of a tissue biopsy shows characteristic findings. What is the diagnosis?

Chromoblastomycosis. ***Chromoblastomycosis*** - **Verrucous skin lesions** are characteristic of chromoblastomycosis, caused by dematiaceous fungi like *Fonsecaea* and *Cladophialophora*. - Microscopic examination reveals pathognomonic **Medlar bodies** (sclerotic bodies/copper pennies) - thick-walled, brown, septate structures that are diagnostic. *Sporotrichosis* - Typically presents with **nodular lymphangitic** spread following trauma, not verrucous lesions. - Microscopy shows **cigar-shaped yeasts** of *Sporothrix schenckii*, not sclerotic bodies. *Rhinosporidiosis* - Characterized by **nasal polyps** and **friable masses** in mucous membranes, not skin verrucous lesions. - Microscopy reveals large **sporangia** containing **endospores** of *Rhinosporidium seeberi*, distinct from Medlar bodies. *Mycetoma* - Presents with **chronic granulomatous** swelling with **sinuses** and **grain discharge**, not verrucous appearance. - Microscopy shows **fungal grains** (white or black) depending on causative organism, not sclerotic bodies.

Q: A patient presents with foot swelling, pus discharge, and multiple sinuses. A KOH smear reveals filamentous structures. What is the most likely diagnosis?

Madura mycosis. ### Explanation The clinical presentation of **foot swelling, multiple discharging sinuses, and pus** is the classic triad of **Mycetoma** (Madura foot). **1. Why Madura Mycosis is correct:** Mycetoma can be caused by either fungi (**Eumycetoma/Madura mycosis**) or bacteria (**Actinomycetoma**). The key diagnostic clue here is the **KOH smear**, which reveals **filamentous structures** (fungal hyphae). In Madura mycosis, these hyphae are typically thick (2-4 μm) and septate. The presence of "grains" in the discharge is also a hallmark, representing colonies of the causative agent (e.g., *Madurella mycetomatis*). **2. Why other options are incorrect:** * **Actinomycosis:** While it also presents with sinuses and "sulfur granules," it typically involves the **cervicofacial region** (lumpy jaw). Under microscopy, *Actinomyces* are Gram-positive, branching, thin filamentous bacteria (not fungi), and are usually anaerobic. * **Osteomyelitis:** While chronic osteomyelitis can cause swelling and sinuses, it would not show filamentous structures on a KOH smear; it is typically caused by pyogenic bacteria like *Staphylococcus aureus*. * **Anthrax:** Cutaneous anthrax presents as a painless **black eschar** with surrounding edema, not chronic discharging sinuses. **3. High-Yield Clinical Pearls for NEET-PG:** * **Triad of Mycetoma:** Soft tissue swelling + Multiple discharging sinuses + Grains in pus. * **Eumycetoma (Fungal):** Caused by *Madurella mycetomatis* (Black grains). Shows thick hyphae on KOH. * **Actinomycetoma (Bacterial):** Caused by *Nocardia* or *Actinomadura*. Shows thin filaments (<1 μm) on Gram stain. * **Radiology:** The **"Dot-in-circle" sign** on MRI is pathognomonic for mycetoma.

Q: Orbital mucormycosis is a complication of -

Diabetic ketoacidosis. ### Explanation **Correct Answer: D. Diabetic ketoacidosis** **Why it is correct:** Orbital Mucormycosis (Rhino-oculo-cerebral mucormycosis) is a life-threatening opportunistic fungal infection caused by fungi of the order Mucorales (e.g., *Rhizopus oryzae*). **Diabetic Ketoacidosis (DKA)** is the most significant risk factor because: 1. **Acidosis:** The fungus possesses an enzyme called **ketone reductase**, which allows it to thrive in acidic, glucose-rich environments. 2. **Iron Availability:** Acidosis causes iron to dissociate from transferrin. Mucorales are "siderophilic" (iron-loving) and use this free iron for rapid growth and angioinvasion. **Why the other options are incorrect:** * **A. AIDS:** While AIDS causes many opportunistic infections (like Cryptococcosis or CMV), Mucormycosis is specifically linked to metabolic derangements (DKA) and neutropenia rather than isolated T-cell deficiency. * **B. Steroid therapy:** Long-term steroids increase the risk of fungal infections by causing hyperglycemia and immunosuppression, but DKA remains the classic, most high-yield association for the *orbital* presentation. * **C. Cushing's disease:** While it causes endogenous hypercortisolism and secondary diabetes, it rarely leads to the acute, severe ketoacidosis required for the rapid fulminant spread of Mucor. **Clinical Pearls for NEET-PG:** * **Hallmark Pathology:** Broad, **non-septate hyphae** with **right-angled (90°) branching**. * **Key Feature:** **Angioinvasion** leading to tissue infarction and the characteristic **black eschar** on the turbinates or palate. * **Clinical Presentation:** Sudden proptosis, internal/external ophthalmoplegia (due to involvement of orbital apex), and vision loss. * **Management:** Medical emergency requiring aggressive surgical debridement and intravenous **Liposomal Amphotericin B**. Control of the underlying DKA is the first step in management.

Q: Which of the following is NOT true about Cryptococcus?

Forms pseudohyphae. **Explanation:** The correct answer is **C (Forms pseudohyphae)**. *Cryptococcus neoformans* is a unique fungus because it is an **obligate yeast**. Unlike most other pathogenic yeasts (such as *Candida*), *Cryptococcus* does not produce pseudohyphae or true hyphae in clinical specimens or standard cultures. It exists solely as a round-to-oval budding yeast. **Analysis of Options:** * **A. Has a polysaccharide capsule:** This is a hallmark feature. *Cryptococcus* is the only medically important fungus with a prominent **glucuronoxylomannan capsule**, which is its primary virulence factor. It is visualized using **India Ink** (negative staining). * **B. Reproduces by budding:** As a yeast, it reproduces via narrow-based budding. * **D. Is urease positive:** *Cryptococcus* species characteristically produce the urease enzyme, which helps differentiate them from other yeasts like *Candida albicans* (which is urease negative). **High-Yield Clinical Pearls for NEET-PG:** * **Source:** Found in soil enriched with **pigeon droppings**. * **Diagnosis:** **India Ink** preparation shows a "halo" (capsule). The most sensitive screening test is the **CrAg (Cryptococcal Antigen)** lateral flow assay. * **Culture:** Grows on **Sabouraud Dextrose Agar (SDA)**; produces creamy white colonies. On **Bird Seed Agar (Niger Seed Agar)**, it produces brown/black colonies due to phenoloxidase activity (melanin production). * **Clinical Presentation:** Most common cause of fungal meningitis in HIV/AIDS patients (CD4 count <100). * **Histopathology:** Highlighted by **Mucicarmine stain** (stains the capsule bright red) and Masson-Fontana (stains melanin).

Q: An AIDS patient with clinical pneumonia has a bronchoalveolar lavage that demonstrates small, "hat-shaped" structures in alveoli that are about the size of an erythrocyte and stain with silver stains. The microorganism involved is most likely which of the following?

Pneumocystis jirovecii. ### Explanation **Correct Answer: D. Pneumocystis jirovecii** The clinical presentation and microscopic findings are classic for **Pneumocystis Pneumonia (PCP)**, an opportunistic infection caused by the fungus *Pneumocystis jirovecii*. * **Why it is correct:** In AIDS patients (typically CD4 < 200 cells/µL), *P. jirovecii* causes interstitial pneumonia. The diagnostic hallmark in bronchoalveolar lavage (BAL) or induced sputum is the presence of **cysts**. These cysts are roughly the size of an erythrocyte (5–8 µm), contain intracystic bodies, and are classically described as **"cup-shaped," "saucer-shaped," or "hat-shaped."** They do not grow on standard fungal media and require special stains like **Gomori Methenamine Silver (GMS)** or Toluidine blue to be visualized. **Analysis of Incorrect Options:** * **A. Aspergillus fumigatus:** Characterized by septate hyphae with acute-angle (45°) branching. It does not form small, hat-shaped cysts. * **B. Blastomyces dermatitidis:** A dimorphic fungus characterized by large, thick-walled yeast cells with **broad-based budding**. * **C. Mycobacterium avium:** An acid-fast bacillus (AFB) that causes systemic illness in advanced AIDS. It appears as slender rods on Ziehl-Neelsen stain, not as silver-staining cysts. **NEET-PG High-Yield Pearls:** * **Stain of choice:** GMS (silver stain) highlights the cyst wall; Giemsa stain highlights the trophic forms (nuclei). * **Radiology:** Characteristically shows bilateral, diffuse **"ground-glass opacities"** extending from the perihilar region. * **Biochemical Marker:** Elevated serum **Beta-D-Glucan** is often seen (non-specific but suggestive). * **Treatment:** First-line therapy and prophylaxis is **Trimethoprim-Sulfamethoxazole (TMP-SMX)**. Steroids are added if $PaO_2 35$ mmHg.

Q: Prolonged use of antibiotics in children can result in which of the following conditions?

Candidiasis. **Explanation:** The correct answer is **B. Candidiasis**. **Mechanism of Action:** The human oral cavity and gastrointestinal tract maintain a delicate balance of normal microbial flora. Broad-spectrum or prolonged antibiotic therapy suppresses the growth of beneficial commensal bacteria (such as *Lactobacillus*). These bacteria normally compete with *Candida albicans* for nutrients and binding sites and maintain an acidic pH that inhibits fungal overgrowth. When this bacterial "interference" is removed, *Candida*—an opportunistic fungus—proliferates, leading to conditions like oral thrush or diaper dermatitis. **Analysis of Incorrect Options:** * **A. Necrotising Ulcerative Gingivitis (NUG):** Also known as "Trench Mouth," this is an acute infection caused by a fuso-spirochetal complex (e.g., *Prevotella intermedia*). It is associated with poor hygiene and immunosuppression, not antibiotic use. In fact, antibiotics are part of its treatment. * **C. Actinomycosis:** This is a chronic granulomatous infection caused by *Actinomyces israelii*. It typically occurs following local trauma (like dental extraction) and is treated with long-term penicillin; it is not caused by antibiotic use. * **D. Aphthous Ulcers:** These are painful, non-infectious oral ulcers. While their exact etiology is idiopathic, they are often linked to stress, trauma, or vitamin deficiencies (B12, Folate), rather than antibiotic-induced flora changes. **High-Yield Clinical Pearls for NEET-PG:** * **Oral Candidiasis (Thrush):** Characterized by white, "curd-like" plaques that **can be scraped off**, leaving an erythematous (bleeding) base. * **Other complications of prolonged antibiotics:** Pseudomembranous colitis (caused by *Clostridioides difficile* overgrowth) and Vitamin K deficiency (due to destruction of gut flora). * **Treatment:** Topical Nystatin or oral Fluconazole are the first-line agents for pediatric candidiasis.

Question 1

Draining sinuses are seen in which of the following conditions?

Accepted Answer

Mycetoma

Answer

Scrofula

Answer

Lupus vulgaris

Answer

Pediculosis

Question 2

A patient with a previous history of tuberculosis complains of hemoptysis. Chest x-ray reveals an upper lobe mass with a cavity and a crescent-shaped air-fluid level. What is the most likely etiologic agent?

Accepted Answer

Aspergillus flavus

Answer

Coccidioides immitis

Answer

Herpes simplex virus type 1

Answer

Herpes simplex virus type 2

Question 3

In an AIDS patient presenting with fever and cough, a diagnosis of Pneumocystis jirovecii pneumonia is best established by?

Accepted Answer

Bronchoalveolar lavage

Answer

Transtracheal biopsy

Answer

Staining for Pneumocystis cysts (e.g., silver stain)

Answer

Sputum aspiration and culture

Question 4

Barrel-shaped spores are seen with which of the following fungi?

Accepted Answer

Coccidioides

Answer

Blastomyces

Answer

Histoplasma

Answer

Candida

Question 5

A 40-year-old male presents with verrucous skin lesions. Microscopic examination of a tissue biopsy shows characteristic findings. What is the diagnosis?

Accepted Answer

Chromoblastomycosis

Answer

Sporotrichosis

Answer

Rhinosporidiosis

Answer

Mycetoma

Question 6

A patient presents with foot swelling, pus discharge, and multiple sinuses. A KOH smear reveals filamentous structures. What is the most likely diagnosis?

Accepted Answer

Madura mycosis

Answer

Osteomyelitis

Answer

Anthrax

Answer

Actinomycosis

Question 7

Orbital mucormycosis is a complication of -

Accepted Answer

Diabetic ketoacidosis

Answer

AIDS

Answer

Steroid therapy

Answer

Cushing's disease

Question 8

Which of the following is NOT true about Cryptococcus?

Accepted Answer

Forms pseudohyphae

Answer

Has a polysaccharide capsule

Answer

Reproduces by budding

Answer

Is urease positive

Question 9

An AIDS patient with clinical pneumonia has a bronchoalveolar lavage that demonstrates small, "hat-shaped" structures in alveoli that are about the size of an erythrocyte and stain with silver stains. The microorganism involved is most likely which of the following?

Accepted Answer

Pneumocystis jirovecii

Answer

Aspergillus fumigatus

Answer

Blastomyces dermatitidis

Answer

Mycobacterium avium

Question 10

Prolonged use of antibiotics in children can result in which of the following conditions?

Accepted Answer

Candidiasis

Answer

Necrotising ulcerative gingivitis

Answer

Actinomycosis

Answer

Aphthous ulcers

Mycology — MCQs

Mycology — MCQs

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