Mycology — MCQs
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Which type of candidiasis is associated with leukoplakia?
Which of the following statements is NOT true about Rhinosporidiosis?
Which of the following is not a fungal infection?
All statements are true about mycetoma except:
Candida infection is predisposed by all of the following, except:
Barrel-shaped arthroconidia are characteristic of which one of the following fungi?
Which of the following statements about Pneumocystis jiroveci is FALSE?
Latex agglutination study of the antigen in CSF helps in the diagnosis of which organism?
Which parasite causes severe malabsorption syndrome?
Meningitis can be caused by which of the following organisms?
Mycology Indian Medical PG Practice Questions and MCQs
Question 201: Which type of candidiasis is associated with leukoplakia?
- A. Acute pseudomembranous candidiasis
- B. Acute atrophic candidiasis
- C. Chronic atrophic candidiasis
- D. Chronic hyperplastic candidiasis (Correct Answer)
Explanation: **Explanation:** **Chronic Hyperplastic Candidiasis (CHC)**, also known as **Candidal Leukoplakia**, is the correct answer because it is the only clinical variant of oral candidiasis that presents as a persistent, white, keratotic plaque. Unlike other forms, these lesions are **non-scrapable** and are histologically characterized by fungal hyphae invading the superficial layers of the oral epithelium, leading to significant hyperplasia. It is considered a premalignant condition, as a small percentage of cases can progress to squamous cell carcinoma. **Analysis of Incorrect Options:** * **Acute Pseudomembranous Candidiasis (Thrush):** Presents as creamy white "curd-like" patches. The defining feature is that these patches **can be scraped off**, leaving an erythematous (bleeding) base. * **Acute Atrophic Candidiasis:** Often associated with broad-spectrum antibiotic use; it presents as a painful, red, "burning" tongue rather than a white plaque. * **Chronic Atrophic Candidiasis (Denture Stomatitis):** Commonly seen under ill-fitting dentures. It is characterized by localized erythema and inflammation of the denture-bearing mucosa, not leukoplakia. **High-Yield Clinical Pearls for NEET-PG:** * **Scrapability:** If the white lesion scrapes off, think **Thrush**; if it does not, think **Leukoplakia/CHC**. * **Risk Factors:** Smoking is a major predisposing factor for the hyperplastic variant. * **Diagnosis:** Periodic Acid-Schiff (PAS) stain is the gold standard to demonstrate fungal hyphae in tissue sections. * **Management:** CHC requires long-term antifungal therapy and regular follow-up due to its malignant potential.
Question 202: Which of the following statements is NOT true about Rhinosporidiosis?
- A. It can be cultured on Sabouraud's dextrose Agar. (Correct Answer)
- B. Fungal spherules are seen in biopsy.
- C. It bleeds to touch.
- D. The most common site is the nose.
Explanation: **Explanation:** Rhinosporidiosis is a chronic granulomatous infection caused by ***Rhinosporidium seeberi***. Despite its name and fungal-like appearance, it is currently classified as an aquatic protistan parasite (Mesomycetozoea). **1. Why Option A is the Correct Answer (The False Statement):** The hallmark characteristic of *Rhinosporidium seeberi* is that it **cannot be cultured** on any artificial microbiological media, including Sabouraud’s Dextrose Agar (SDA). It has never been successfully grown *in vitro*. Diagnosis relies entirely on clinical presentation and histopathology. **2. Analysis of Other Options:** * **Option B (Fungal spherules):** Histopathology is diagnostic. It reveals large, thick-walled **sporangia (spherules)** measuring up to 350 µm, filled with thousands of tiny **endospores**. This is a classic "high-yield" pathology finding. * **Option C (Bleeds to touch):** Clinically, it presents as friable, leafy, or strawberry-like polypoid masses. Due to high vascularity, these lesions **bleed profusely** upon minor trauma or touch. * **Option D (Most common site):** The **nasal mucosa** (nasal septum and floor) is the most common site of involvement (approx. 70%), followed by the nasopharynx and conjunctiva. **Clinical Pearls for NEET-PG:** * **Epidemiology:** Highly prevalent in South India (Tamil Nadu, Kerala) and Sri Lanka; associated with bathing in stagnant pond water. * **Transmission:** Traumatic inoculation of spores from contaminated water. * **Treatment:** Wide surgical excision with **electrocautery** of the base to prevent recurrence. Dapsone is sometimes used as an adjunct. * **Staining:** Sporangia can be visualized with H&E, GMS, and PAS stains.
Question 203: Which of the following is not a fungal infection?
- A. Rhinosporidiosis (Correct Answer)
- B. Sporotrichosis
- C. Torulosis
- D. Candidiasis
Explanation: **Explanation:** The correct answer is **Rhinosporidiosis**. Historically, *Rhinosporidium seeberi* was classified as a fungus due to its morphology (presence of sporangia and spores). However, modern molecular phylogenetic analysis has reclassified it as a **Mesomycetozoean**, a group of aquatic protists (parasites) located at the evolutionary boundary between animals and fungi. It primarily causes chronic granulomatous lesions, typically presenting as friable, leafy, strawberry-like polyps in the nasal cavity. **Analysis of Incorrect Options:** * **Sporotrichosis:** Caused by the dimorphic fungus *Sporothrix schenckii*. It is often called "Rose gardener’s disease" and typically presents with lymphocutaneous nodules. * **Torulosis:** This is an archaic synonym for **Cryptococcosis**, caused by the encapsulated yeast *Cryptococcus neoformans*. It is a major cause of fungal meningitis in immunocompromised patients. * **Candidiasis:** Caused by *Candida* species (most commonly *C. albicans*), which are opportunistic yeast-like fungi responsible for conditions ranging from oral thrush to systemic candidemia. **High-Yield Clinical Pearls for NEET-PG:** * **Rhinosporidiosis:** Look for a history of bathing in stagnant water. The characteristic histopathology shows large **sporangia** (up to 350 µm) containing thousands of **endospores**. It cannot be cultured on artificial media. * **Treatment of choice:** Surgical excision with electrocautery of the base. * **Differential Diagnosis:** Do not confuse Rhinosporidiosis with *Coccidioidomycosis*; both show endosporulating spherules, but *Coccidioides* spherules are much smaller (up to 60 µm).
Question 204: All statements are true about mycetoma except:
- A. Eumycetoma is caused by bacteria (Correct Answer)
- B. Surgery is an important component of treatment
- C. It is usually painless
- D. Diagnosis can be made by examination of the lesion
Explanation: **Explanation:** The correct answer is **A**. Mycetoma is a chronic, granulomatous, subcutaneous infection characterized by a triad of localized swelling, underlying bone destruction, and the presence of discharging sinuses containing grains. It is classified into two types based on the causative agent: 1. **Eumycetoma:** Caused by **fungi** (e.g., *Madurella mycetomatis*). 2. **Actinomycetoma:** Caused by **filamentous bacteria** (e.g., *Nocardia*, *Actinomadura*). Therefore, the statement that Eumycetoma is caused by bacteria is false. **Analysis of other options:** * **Option B:** Surgery is often necessary for Eumycetoma, as fungal cases respond poorly to medical therapy alone. Wide local excision or amputation may be required. In contrast, Actinomycetoma is primarily managed with antibiotics (Welsh regimen). * **Option C:** Mycetoma is typically a **painless** lesion despite significant swelling and deformity. Pain usually only occurs with secondary bacterial infection or deep bone involvement. * **Option D:** Diagnosis is clinically suspected by the presence of the triad and confirmed by examining the **grains** (sulfur granules) discharged from the sinuses. The color, size, and consistency of these grains provide clues to the specific causative agent. **NEET-PG High-Yield Pearls:** * **Madura Foot:** The common clinical name for mycetoma. * **Grains:** Black grains are pathognomonic for **fungal** (Eumycetoma) etiology. * **Welsh Regimen:** The gold standard treatment for Actinomycetoma (Amikacin + Cotrimoxazole). * **Radiology:** "Dot-in-circle" sign on MRI is a highly specific diagnostic feature.
Question 205: Candida infection is predisposed by all of the following, except:
- A. Menstruation (Correct Answer)
- B. Diabetes
- C. Minipill users
- D. Combined pill users
Explanation: **Explanation:** The correct answer is **Menstruation**. *Candida albicans* is a dimorphic fungus that exists as a commensal in the vaginal flora. Its transition into a pathogen (causing Vulvovaginal Candidiasis) is heavily dependent on the vaginal environment, specifically **high estrogen levels** and **low pH**. **1. Why Menstruation is the correct answer:** During menstruation, estrogen levels drop significantly, and the vaginal pH becomes more alkaline (due to the presence of blood). *Candida* thrives in an acidic environment (pH < 4.5). Furthermore, the menstrual flow physically flushes out the yeast. Therefore, symptoms of Candidiasis typically **improve** during menstruation and worsen just before (premenstrual phase). **2. Why the other options are incorrect:** * **Diabetes Mellitus:** Hyperglycemia leads to increased glycogen content in vaginal epithelial cells and high glucose in secretions, providing an ideal substrate for fungal growth and adherence. * **Combined Oral Contraceptive Pills (COCPs):** These contain high doses of estrogen, which increases vaginal glycogen. This glycogen is fermented by *Lactobacilli* into lactic acid. While *Candida* likes acid, the high glycogen and estrogen-induced changes in the epithelium are potent triggers for colonization. * **Minipill (Progestogen-only pill):** While less potent than COCPs, hormonal fluctuations and changes in cervical mucus associated with exogenous steroids can still disrupt the local microbiome, predisposing to overgrowth compared to non-users. **High-Yield Clinical Pearls for NEET-PG:** * **Risk Factors for Candidiasis:** Pregnancy (high estrogen), Broad-spectrum antibiotics (kill protective *Lactobacilli*), Immunosuppression (HIV/Steroids), and Uncontrolled Diabetes. * **Diagnosis:** Look for "Curdy white/Cottage cheese" discharge and **pseudohyphae** on KOH mount. * **Vaginal pH:** In Candidiasis, the pH is typically **normal (<4.5)**, unlike Trichomoniasis or Bacterial Vaginosis where pH is >4.5.
Question 206: Barrel-shaped arthroconidia are characteristic of which one of the following fungi?
- A. E. floccosum
- B. C. immitis (Correct Answer)
- C. Phialophora verrucosa
- D. M. canis
Explanation: **Explanation:** The correct answer is **Coccidioides immitis**. **1. Why C. immitis is correct:** *Coccidioides immitis* is a dimorphic fungus that exists in nature (soil) as a mold. It produces highly infectious, thick-walled, **barrel-shaped arthroconidia** (arthrospores). A key diagnostic feature is that these arthroconidia alternate with empty "disjunctor cells," giving them a characteristic **"checkerboard" appearance** under the microscope. When inhaled by a human, these arthroconidia transform into large, thick-walled **spherules** containing endospores in the lungs. **2. Why the other options are incorrect:** * **Epidermophyton floccosum:** A dermatophyte characterized by large, smooth-walled, **club-shaped (pyriform) macroconidia** arranged in clusters (often compared to "beaver tails"). It does not produce barrel-shaped arthroconidia. * **Phialophora verrucosa:** One of the causative agents of Chromoblastomycosis. It is characterized by **vase-shaped phialides** with a distinct collarette, producing oval conidia. * **Microsporum canis:** A zoophilic dermatophyte known for its spindle-shaped, thick-walled **macroconidia with curved/hooked ends** and more than six internal cells. **3. NEET-PG High-Yield Pearls:** * **Coccidioidomycosis** is also known as **Valley Fever** or Desert Rheumatism (endemic to SW USA/Mexico). * **Safety Warning:** *C. immitis* is highly laboratory-contagious; cultures must be handled in a Biosafety Level 3 (BSL-3) facility. * **Diagnostic Triad:** Barrel-shaped arthroconidia (in vitro/soil) → Spherules with endospores (in vivo/tissue). * **E. floccosum** is unique among dermatophytes because it **never produces microconidia**.
Question 207: Which of the following statements about Pneumocystis jiroveci is FALSE?
- A. It is typically seen only in immunocompromised individuals.
- B. It is frequently associated with Cytomegalovirus (CMV). (Correct Answer)
- C. It may be associated with the development of a pneumatocele.
- D. It is diagnosed using sputum microscopy.
Explanation: **Explanation:** *Pneumocystis jirovecii* (formerly *P. carinii*) is a unique unicellular fungus that primarily causes **Pneumocystis Pneumonia (PCP)** in immunocompromised hosts. **Why Option B is the Correct (False) Statement:** While both *P. jirovecii* and Cytomegalovirus (CMV) are common opportunistic infections in HIV/AIDS patients, there is **no specific or frequent pathological association** between the two. They are independent co-infections. The presence of one does not inherently necessitate or predict the presence of the other, making this statement the false one among the choices. **Analysis of Other Options:** * **Option A:** *P. jirovecii* is an opportunistic pathogen. It rarely causes disease in healthy individuals but is a defining illness in patients with low CD4 counts (<200 cells/µL), transplant recipients, or those on long-term steroids. * **Option C:** PCP is known for causing interstitial inflammation which can lead to subpleural blebs or **pneumatoceles** (air-filled cysts). Rupture of these cysts can lead to spontaneous pneumothorax, a known complication. * **Option D:** Diagnosis is primarily microscopic. While **induced sputum** can be used, it has lower sensitivity than Bronchoalveolar Lavage (BAL). Organisms are visualized using **Gomori Methenamine Silver (GMS)** stain (shows crushed-cup shaped cysts) or Direct Fluorescent Antibody (DFA) testing. **High-Yield Clinical Pearls for NEET-PG:** * **Classification:** It was previously classified as a protozoan but is now a **fungus** based on nucleic acid analysis (lacks ergosterol in the cell membrane). * **Drug of Choice:** **Trimethoprim-Sulfamethoxazole (TMP-SMX)**. * **Radiology:** Classic "Ground-glass opacities" (GGO) and perihilar infiltrates on X-ray/CT. * **Biomarker:** Elevated **Serum Beta-D-Glucan** is a sensitive but non-specific marker for PCP.
Question 208: Latex agglutination study of the antigen in CSF helps in the diagnosis of which organism?
- A. Cryptococcus (Correct Answer)
- B. Candidiasis
- C. Aspergillosis
- D. Histoplasmosis
Explanation: **Explanation:** **Cryptococcus neoformans** is the correct answer because it possesses a unique, thick **polysaccharide capsule** (composed primarily of Glucuronoxylomannan). In cases of Cryptococcal meningitis, this capsular antigen is shed in high concentrations into the Cerebrospinal Fluid (CSF). The **Latex Agglutination Test (LAT)** utilizes latex beads coated with specific antibodies to detect this antigen. It is highly sensitive (>90%) and specific, often providing a diagnosis faster than a fungal culture and being more sensitive than an India Ink preparation. **Why other options are incorrect:** * **Candidiasis:** Diagnosis typically relies on blood culture, KOH mount (pseudohyphae), or the β-D-Glucan assay. While antigen tests exist (Mannan antigen), LAT of CSF is not a standard diagnostic modality. * **Aspergillosis:** The primary biomarker for invasive aspergillosis is the **Galactomannan antigen**, usually detected via ELISA in serum or Bronchoalveolar Lavage (BAL) fluid, not LAT of CSF. * **Histoplasmosis:** Diagnosis is generally made through fungal culture, histopathology (showing intracellular yeast in macrophages), or urinary/serum antigen testing (EIA), but not typically via CSF latex agglutination. **High-Yield Clinical Pearls for NEET-PG:** * **India Ink:** Shows a "clear halo" against a dark background (negative staining); however, it is less sensitive than LAT. * **Culture:** Sabouraud Dextrose Agar (SDA) shows creamy white mucoid colonies. * **Biochemical test:** Cryptococcus is **Urease positive** and produces melanin on **Bird Seed Agar** (Niger seed agar). * **Histopathology:** The capsule stains bright red with **Mucicarmine** or PAS. * **Risk Factor:** Strongly associated with low CD4 counts (<100 cells/μL) in HIV/AIDS patients.
Question 209: Which parasite causes severe malabsorption syndrome?
- A. Giardiasis (Correct Answer)
- B. Hookworm
- C. Ascariasis
- D. Amoebiasis
Explanation: **Explanation:** **Giardiasis (Option A)** is the correct answer. *Giardia lamblia* is a flagellated protozoan that colonizes the duodenum and jejunum. It causes malabsorption by adhering to the intestinal mucosa via a ventral sucking disc. This leads to **villous atrophy**, blunting of microvilli, and a physical barrier effect that prevents nutrient absorption. Specifically, it causes a deficiency of disaccharidases (like lactase), leading to **steatorrhea** (foul-smelling, fatty stools) and significant weight loss. **Why the other options are incorrect:** * **Hookworm (Option B):** Primarily causes **Iron Deficiency Anemia** due to chronic blood loss from the intestinal wall. While heavy infections can cause protein loss, malabsorption is not the hallmark feature. * **Ascariasis (Option C):** Usually causes intestinal obstruction (bolus of worms) or Loeffler’s syndrome (pulmonary phase). It competes for nutrients but does not typically cause a formal malabsorption syndrome. * **Amoebiasis (Option D):** *Entamoeba histolytica* causes flask-shaped ulcers and tissue destruction leading to bloody diarrhea (dysentery) rather than malabsorption. **NEET-PG High-Yield Pearls:** * **Habitat:** Duodenum and upper Jejunum (Acidic environment). * **Diagnosis:** Stool microscopy (Cysts/Trophozoites) or **String Test (Entero-test)**. * **Morphology:** Trophozoite is "Pear-shaped" with "Falling leaf motility" and "Owl’s eye appearance" on staining. * **Association:** Increased prevalence in patients with **Common Variable Immunodeficiency (CVID)** due to IgA deficiency. * **Drug of Choice:** Tinidazole or Metronidazole.
Question 210: Meningitis can be caused by which of the following organisms?
- A. Sporothrix
- B. Mucor
- C. Rhizopus
- D. Cryptococcus neoformans (Correct Answer)
Explanation: ### Explanation **Correct Answer: D. Cryptococcus neoformans** **Why it is correct:** *Cryptococcus neoformans* is an encapsulated yeast and the most common fungal cause of meningitis, particularly in immunocompromised individuals (e.g., HIV/AIDS patients with CD4 counts <100 cells/µL). The fungus is typically inhaled from the environment (often associated with pigeon droppings) and undergoes hematogenous dissemination from the lungs to the central nervous system (CNS). Its thick polysaccharide capsule allows it to evade the immune system and cross the blood-brain barrier, leading to subacute or chronic meningitis. **Why the other options are incorrect:** * **A. Sporothrix schenckii:** This is a dimorphic fungus that primarily causes **Sporotrichosis** (Rose gardener’s disease), characterized by subcutaneous nodules following the lymphatic drainage. While disseminated disease can occur in rare cases, it is not a classic cause of meningitis. * **B & C. Mucor and Rhizopus:** These belong to the order Mucorales. They are known for causing **Rhinocerebral Mucormycosis**, especially in patients with uncontrolled diabetes (ketoacidosis) or neutropenia. While they are highly invasive and can spread from the sinuses to the brain, they typically cause **cerebral infarction and necrosis** (angioinvasion) rather than meningitis. **High-Yield Clinical Pearls for NEET-PG:** * **Diagnosis:** India Ink preparation of CSF shows a "halo" (negative staining of the capsule). * **Most Sensitive Test:** Cryptococcal Antigen (CrAg) detection via Latex Agglutination or Lateral Flow Assay. * **Culture:** Sabouraud Dextrose Agar (SDA) produces creamy, mucoid colonies; Niger seed agar (Birdseed agar) produces brown/black colonies due to phenoloxidase activity. * **Histopathology:** Mucicarmine stain specifically stains the capsule bright red. * **Treatment:** Induction with Amphotericin B + Flucytosine, followed by Fluconazole for maintenance.
Practice by Chapter
Classification of Fungi
Practice Questions
Superficial Mycoses
Practice Questions
Dermatophytes
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Subcutaneous Mycoses
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Candidiasis
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Aspergillosis
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Cryptococcosis
Practice Questions
Zygomycosis
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Endemic Mycoses
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Opportunistic Fungal Infections
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Antifungal Agents
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Laboratory Diagnosis of Fungal Infections
Practice Questions
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