Fungal Infections — MCQs
A man has undergone renal transplant and is taking immunosuppressant drug. On biopsy there was presence of budding cells with pseudohyphae. Identify the organism?
Amphotericin B acts on:-
Histoplasma capsulatum, a dimorphic fungus found in soil heavily contaminated with bird droppings, is identified in tissue biopsies by which of the following characteristics?
Regarding fungal cell wall, all are true except:
A biopsy of a lung nodule from a patient with a history of bird exposure reveals yeast cells with thick capsules. What is the most likely pathogen?
Broad-based budding yeasts are seen in:
A 45-year-old patient with a history of poorly controlled diabetes presents with sinus pain, nasal discharge, and facial swelling. A biopsy reveals broad, nonseptate hyphae branching at wide angles. What is the most likely causative agent?
An 8-year-old child has localized non-cicatricial alopecia over scalp with itching and scales. The diagnosis is :
A 70 year old farmer, presented to you with complaints of yellowish discolouration of his finger nails for the past 6 months, he also gives history of recurrent episodes of itching in the groin for which he used to take local home made herbal remedy. On examination 3 of his toe nails also show similar change with tunneling. Which among the following is the best test for rapid confirmation of your diagnosis?
A plant prick can produce sporotrichosis. Which of the following statements about sporotrichosis is false?
Fungal Infections Indian Medical PG Practice Questions and MCQs
Question 1: A man has undergone renal transplant and is taking immunosuppressant drug. On biopsy there was presence of budding cells with pseudohyphae. Identify the organism?
- A. Invasive candidiasis (Correct Answer)
- B. Pneumocystis
- C. Invasive aspergillosis
- D. Histoplasmosis
Explanation: ***Invasive candidiasis*** - The presence of **budding cells** and **pseudohyphae** on biopsy is a classic histological finding for *Candida* species. - Individuals who have undergone **renal transplant** and are on **immunosuppressant drugs** are at high risk for opportunistic fungal infections, including invasive candidiasis. *Pneumocystis* - *Pneumocystis jirovecii* typically causes pneumonia and is characterized by cysts or trophic forms in lung tissue, not budding cells and pseudohyphae. - While common in immunocompromised patients, its microscopic morphology is distinctly different from *Candida*. *Invasive aspergillosis* - *Aspergillus* species are characterized by **septate hyphae with acute angle branching** (typically 45-degree angles) on microscopy. - They do not form budding cells or pseudohyphae, which are characteristic of *Candida*. *Histoplasmosis* - *Histoplasma capsulatum* appears as **small, oval-shaped yeast cells** (2-4 µm) often found within macrophages. - It does not form pseudohyphae or large budding cells as described in the question.
Question 2: Amphotericin B acts on:-
- A. Cell membrane (Correct Answer)
- B. Cytoplasm
- C. Nucleus
- D. Cell wall
Explanation: ***Cell membrane*** Amphotericin B primarily targets the **ergosterol** in the fungal **cell membrane** [1]. It binds to **ergosterol**, forming pores and disrupting the membrane's integrity, leading to leakage of cellular contents and ultimately cell death [1]. *Cytoplasm* The cytoplasm is the internal fluid of the cell where many metabolic processes occur, but it is **not the primary target** of amphotericin B's fungicidal action. While cytoplasmic contents leak out due to membrane damage, the drug does not directly act on cytoplasmic components to exert its effect. *Nucleus* The nucleus contains the genetic material of the fungal cell, but amphotericin B does **not directly interact with nuclear components** or DNA. Damage to the cell membrane is the primary mechanism, with nuclear function only indirectly affected by overall cellular disruption. *Cell wall* Fungal cell walls are composed of **chitin and glucans**, but amphotericin B **does not target these components**. Its action is distinct from drugs that inhibit cell wall synthesis, such as echinocandins.
Question 3: Histoplasma capsulatum, a dimorphic fungus found in soil heavily contaminated with bird droppings, is identified in tissue biopsies by which of the following characteristics?
- A. Yeasts with broad-based buds
- B. Single-cell yeasts with pseudohyphae
- C. Arthrospores
- D. Oval budding yeasts within macrophages (Correct Answer)
Explanation: ***Oval budding yeasts within macrophages*** - In tissue biopsies, **Histoplasma capsulatum** characteristically appears as small, **oval-shaped budding yeasts** that are predominantly found **intracellularly within macrophages**. - This intracellular location is a key diagnostic feature, as the organism can survive and multiply inside these phagocytic cells. *Yeasts with broad-based buds* - This description is characteristic of **Blastomyces dermatitidis**, another dimorphic fungus, which displays large yeasts with a single broad-based bud in tissue. - Unlike *Histoplasma*, **Blastomyces** yeasts are typically much larger and not necessarily intracellular. *Single-cell yeasts with pseudohyphae* - This morphology is characteristic of **Candida albicans**, particularly in its pathogenic forms within tissues. - **Candida** forms true hyphae and pseudohyphae, and its yeasts do not typically reside within macrophages in the same manner as *Histoplasma*. *Arthrospores* - **Arthrospores** (also called arthroconidia) are characteristic of fungi like **Coccidioides immitis**, which appear as barrel-shaped structures in laboratory cultures, but *spherules containing endospores* are seen in tissue. - **Histoplasma** does not form arthrospores in human tissue; it forms yeasts.
Question 4: Regarding fungal cell wall, all are true except:
- A. Contains chitin
- B. Prevent osmotic damage
- C. Does not contain peptidoglycan
- D. Azoles act on them (Correct Answer)
Explanation: ***Azoles act on them*** - **Azole antifungals** primarily target the **ergosterol synthesis** pathway, specifically inhibiting the **lanosterol 14-alpha-demethylase** enzyme, which is located in the fungal cell membrane, not the cell wall. - While the cell wall is crucial for fungal viability, agents targeting it (e.g., **echinocandins**) are distinct from azoles. *Contains chitin* - The fungal cell wall is indeed a complex structure composed of various carbohydrates, with **chitin** being a major structural polysaccharide that provides rigidity. - Chitin is a **beta-(1,4)-linked polymer of N-acetylglucosamine** and is a unique component distinguishing fungal cells from animal cells. *Prevent osmotic damage* - The rigid fungal cell wall provides structural support and protects the cell from **environmental stresses**, particularly **osmotic lysis** in hypotonic environments. - It maintains the cell's integrity against internal **turgor pressure**, which is essential for fungal growth and survival. *Does not contain peptidoglycan* - Fungal cell walls are distinct from bacterial cell walls in their composition; they **do not contain peptidoglycan**. - **Peptidoglycan** is a characteristic component of bacterial cell walls, which is targeted by antibiotics like penicillins.
Question 5: A biopsy of a lung nodule from a patient with a history of bird exposure reveals yeast cells with thick capsules. What is the most likely pathogen?
- A. Aspergillus fumigatus
- B. Blastomyces dermatitidis
- C. Histoplasma capsulatum
- D. Cryptococcus neoformans (Correct Answer)
Explanation: ***Cryptococcus neoformans*** - The presence of **yeast cells with thick capsules** is a classic histological finding for *Cryptococcus neoformans*. - While *Cryptococcus* commonly affects immunocompromised individuals, it can also be found in **bird droppings**, particularly from pigeons, making the history of bird exposure relevant. *Aspergillus fumigatus* - *Aspergillus fumigatus* typically presents as **hyphae**, not yeast cells, and would not have a thick capsule. - Infections often manifest as **aspergillomas** (fungus balls) in lung cavities or invasive disease in immunocompromised patients. *Blastomyces dermatitidis* - *Blastomyces dermatitidis* appears as **large, broad-based budding yeast cells** but does not possess a thick capsule. - It is typically found in the **soil**, especially in moist areas, and its association with bird exposure is not as strong as with *Cryptococcus*. *Histoplasma capsulatum* - *Histoplasma capsulatum* is characterized by **small intracellular yeast forms** within macrophages and does not have a thick capsule. - It is strongly associated with **bird and bat droppings** but its microscopic appearance is distinct from that described.
Question 6: Broad-based budding yeasts are seen in:
- A. Histoplasmosis
- B. Blastomycosis (Correct Answer)
- C. Candidiasis
- D. Coccidioidomycosis
Explanation: ***Blastomycosis*** - This fungal infection is classically characterized by **broad-based budding yeasts** seen on microscopic examination. - The yeast cells are typically large and have a characteristic wide connection between the mother and daughter cells during budding. *Histoplasmosis* - Characterized by **small, intracellular yeasts** often seen within macrophages. - These yeasts do **not exhibit broad-based budding**. *Candidiasis* - Primarily presents as **pseudohyphae** (elongated yeast cells resembling hyphae) and budding yeasts (blastoconidia) with **narrow bases**. - **True hyphae** may also be present depending on the species and growth conditions. *Coccidioidomycosis* - In tissue, it is characterized by **spherules** containing **endospores**, not budding yeasts. - The mycelial form is found in culture or environmental samples.
Question 7: A 45-year-old patient with a history of poorly controlled diabetes presents with sinus pain, nasal discharge, and facial swelling. A biopsy reveals broad, nonseptate hyphae branching at wide angles. What is the most likely causative agent?
- A. Aspergillus fumigatus
- B. Rhizopus spp. (Correct Answer)
- C. Candida albicans
- D. Cryptococcus neoformans
Explanation: ***Rhizopus spp.*** - The patient's presentation with **sinus pain**, **nasal discharge**, **facial swelling**, and a history of **poorly controlled diabetes** is classic for **mucormycosis** (also known as zygomycosis). - **Biopsy findings** of **broad, nonseptate hyphae branching at wide/irregular angles** are pathognomonic for mucormycosis, most commonly caused by *Rhizopus* species. - Diabetes mellitus, particularly when poorly controlled with **ketoacidosis**, is a major risk factor for rhinocerebral mucormycosis. *Aspergillus fumigatus* - This fungus typically causes infections with **septate hyphae** that **branch at acute angles** (45 degrees), which is morphologically distinct from mucormycosis. - While *Aspergillus* can cause invasive sinusitis in immunocompromised patients, the specific hyphal morphology (nonseptate, wide-angle branching) points away from it. *Candida albicans* - *Candida albicans* is a yeast that typically appears as **oval budding cells** and **pseudohyphae** on microscopy, not broad, nonseptate hyphae. - While it can cause opportunistic infections in diabetic and immunocompromised patients, its microscopic appearance is entirely inconsistent with the biopsy findings. *Cryptococcus neoformans* - *Cryptococcus neoformans* is an **encapsulated yeast** that is typically identified by its **spherical or oval budding cells** with a characteristic **polysaccharide capsule** visible with India ink stain. - It primarily causes **meningitis** and pulmonary infections in immunocompromised hosts, and its morphology (yeast, not hyphae) is entirely different from the described findings.
Question 8: An 8-year-old child has localized non-cicatricial alopecia over scalp with itching and scales. The diagnosis is :
- A. Lichen planus
- B. Tinea Capitis (Correct Answer)
- C. Tinea Barbae
- D. Alopecia areata
Explanation: ***Tinea Capitis*** - **Tinea capitis** typically presents as **localized, non-cicatricial alopecia** with features like **scaling**, **itching**, and broken hairs, which are consistent with the child's symptoms. - It's a common **dermatophyte infection** of the scalp, particularly in children, caused by fungi like *Trichophyton* or *Microsporum*. *Lichen planus* - **Lichen planus** can cause alopecia, but it is typically a **cicatricial (scarring)** alopecia, unlike the non-cicatricial finding described. - It is more commonly associated with **purplish, polygonal, pruritic papules** on the skin and mucous membranes. *Tinea Barbae* - **Tinea barbae** specifically affects the **beard and mustache area** in adult males and would not present as alopecia on the scalp in an 8-year-old child. - It usually involves deep follicular inflammation with **pustules and nodules**. *Alopecia areata* - **Alopecia areata** is characterized by **smooth, circular patches of non-scarring hair loss** without associated scaling or significant itching. - The presence of **scaling and itching** in this case makes alopecia areata less likely.
Question 9: A 70 year old farmer, presented to you with complaints of yellowish discolouration of his finger nails for the past 6 months, he also gives history of recurrent episodes of itching in the groin for which he used to take local home made herbal remedy. On examination 3 of his toe nails also show similar change with tunneling. Which among the following is the best test for rapid confirmation of your diagnosis?
- A. Tzanck smear
- B. KOH mount (Correct Answer)
- C. Woods lamp
- D. Biopsy
Explanation: ***KOH mount*** - A **KOH mount** (potassium hydroxide) dissolves keratinocytes, allowing for direct visualization of fungal elements such as **hyphae** and **spores** under a microscope. This is the **most rapid and cost-effective test** for confirming fungal infections like **onychomycosis**. - The patient's presentation with **yellowish discoloration** and **"tunneling"** of nails (suggesting onycholysis and subungual hyperkeratosis), along with a history of recurrent groin itching (potentially **tinea cruris**), strongly points to a fungal infection. *Tzanck smear* - A **Tzanck smear** is primarily used to detect multinucleated giant cells in **herpesvirus infections** (e.g., herpes simplex, varicella-zoster). - It is not useful for identifying fungal elements responsible for nail discoloration or suspected onychomycosis. *Woods lamp* - A **Woods lamp** uses ultraviolet light to detect specific fluorescent substances, particularly useful for diagnosing certain **bacterial infections** (e.g., *Corynebacterium minutissimum* in erythrasma) or some **tinea capitis** species (*Microsporum*). - Most common dermatophytes causing onychomycosis **do not fluoresce** under a Wood's lamp, making it an unreliable diagnostic tool in this scenario. *Biopsy* - A **nail biopsy** (with histology and special stains like PAS) is a highly accurate diagnostic method for onychomycosis, especially when other tests are inconclusive. - However, it is an **invasive procedure**, takes more time for results, and is generally not the **most rapid** initial test compared to a KOH mount.
Question 10: A plant prick can produce sporotrichosis. Which of the following statements about sporotrichosis is false?
- A. Enlarged lymph nodes extending centripetally as a beaded chain are a characteristic finding
- B. Most cases are acquired via cutaneous inoculation
- C. It is an occupational disease of butchers, doctors (Correct Answer)
- D. Is a chronic mycotic disease that typically involves skin, subcutaneous tissue and regional lymphatics
Explanation: ***It is an occupational disease of butchers, doctors*** - Sporotrichosis is an **occupational hazard for gardeners, florists, and agricultural workers** due to exposure to decaying plant matter, not typically for butchers or doctors. - The disease is caused by **direct inoculation** of the fungus *Sporothrix schenckii* into the skin, often through a thorn prick or minor trauma. *Most cases are acquired via cutaneous inoculation* - This statement is **true** as sporotrichosis is primarily caused by **traumatic implantation** of fungal spores into the skin. - Common sources include **thorns, splinters, sphagnum moss**, and other plant materials. *Enlarged lymph nodes extending centripetally as a beaded chain are a characteristic finding* - This statement is **true** and describes the classic **lymphocutaneous sporotrichosis**, where lesions and **nodular lymphangitis** track along lymphatic channels. - The "beaded chain" appearance refers to the multiple subcutaneous nodules formed along the lymphatic vessels. *Is a chronic mycotic disease that typically involves skin, subcutaneous tissue and regional lymphatics* - This statement is **true** because sporotrichosis is a **slow-progressing fungal infection** that primarily affects the skin, the tissue just beneath the skin, and the lymphatics draining the infected area. - While systemic dissemination can occur in immunocompromised individuals, the **cutaneous and lymphocutaneous forms** are most common.
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