Mycology Practice Questions

Q: Which statement is false regarding Cryptococcus neoformans?

Urease negative. **Explanation:** *Cryptococcus neoformans* is an encapsulated yeast primarily associated with pigeon droppings and is a significant opportunistic pathogen in immunocompromised patients (e.g., HIV/AIDS). **1. Why "Urease negative" is the False Statement:** *Cryptococcus neoformans* is characteristically **Urease positive**. The production of the urease enzyme is a key biochemical marker used in the laboratory to differentiate it from other yeasts like *Candida albicans* (which is urease negative). It hydrolyzes urea to produce ammonia, raising the pH and changing the indicator color. **2. Analysis of Other Options:** * **Option A (Grows at 5°C and 37°C):** This is true. Unlike many other pathogenic fungi, *C. neoformans* can grow at 37°C (essential for human pathogenicity) and also at lower temperatures like 4°C–5°C. * **Option B (Has 4 serotypes):** This is true. Based on capsular polysaccharide antigens, it is classified into four serotypes: **A, B, C, and D**. (Note: Serotype A is *C. neoformans var. grubii*, while B and C are now often classified as *C. gattii*). * **Option D (Causes superficial skin infection):** This is true. While meningitis is the most common presentation, primary or secondary cutaneous cryptococcosis can occur, presenting as papules, pustules, or ulcerations. **High-Yield Clinical Pearls for NEET-PG:** * **Virulence Factor:** The **Polysaccharide capsule** (Glucuronoxylomannan) is the most important; it inhibits phagocytosis. * **Staining:** **India Ink** preparation shows a "halo" (negative staining). **Mucicarmine** stains the capsule red. * **Culture:** Grows on **Bird Seed Agar** (Niger Seed Agar) producing brown/black colonies due to **Phenoloxidase** activity (melanin production). * **Drug of Choice:** Induction with Amphotericin B + Flucytosine, followed by Fluconazole.

Q: About 90 days post-bone marrow transplant, a 55-year-old white woman began to complain of dry cough, shortness of breath, and chest pain. She was started on antibiotics and blood culture obtained at the time was negative and there was not improvement. A computed tomography (CT) scan of the lungs showed a halo of low attenuation around a nodular lesion. Analysis of lung biopsy was similar to methenamine silver-stained section below. What is the most likely diagnosis for this patient?

Aspergillosis. ***Aspergillosis*** - **Halo sign** on CT (low attenuation around nodular lesion) is **pathognomonic** for invasive pulmonary aspergillosis in immunocompromised patients post-bone marrow transplant. - **GMS stain** reveals characteristic **septate hyphae** with **acute-angle branching** (45°), typical of *Aspergillus* species. *Candidiasis* - Typically presents as **disseminated candidemia** or **oral thrush** rather than pulmonary nodules with halo sign in post-BMT patients. - **GMS stain** would show **pseudohyphae** and **budding yeast cells**, not septate hyphae with acute branching. *Histoplasmosis* - More common in **endemic areas** (Ohio/Mississippi river valleys) and typically causes **diffuse pulmonary infiltrates**, not nodular lesions with halo sign. - **GMS stain** reveals **small intracellular yeasts** within macrophages, not septate hyphae. *Mucormycosis* - Though seen in immunocompromised patients, typically causes **rhinocerebral** or **pulmonary** disease with **tissue necrosis** and black eschar. - **GMS stain** shows **non-septate hyphae** with **wide-angle branching** (90°), contrasting with Aspergillus morphology.

Q: Brown, spherical, septate bodies found in pus are diagnostic of which condition?

Chromomycosis. **Explanation:** The presence of **brown, spherical, thick-walled, septate bodies** (also known as **Sclerotic bodies**, **Medlar bodies**, or **Copper-penny bodies**) in pus or tissue sections is the pathognomonic hallmark of **Chromomycosis** (Chromoblastomycosis). These structures represent the vegetative fungal form and are naturally pigmented due to melanin in their cell walls (dematiaceous fungi). **Why the other options are incorrect:** * **Geotrichosis:** Caused by *Geotrichum candidum*, it typically shows rectangular arthroconidia and true hyphae, not pigmented spherical bodies. * **Mucormycosis:** Characterized by broad, **non-septate (coenocytic)**, ribbon-like hyphae with right-angle (90°) branching. * **Sporotrichosis:** Caused by *Sporothrix schenckii*, it typically presents as **cigar-shaped yeast** cells in tissue. The characteristic clinical finding is "sporotrichoid spread" (nodules along lymphatic drainage). **High-Yield Clinical Pearls for NEET-PG:** * **Causative Agents:** Most commonly *Fonsecaea pedrosoi* and *Phialophora verrucosa*. * **Clinical Presentation:** Usually occurs in barefoot agricultural workers following traumatic inoculation. It presents as slow-growing, **verrucous (warty) plaques** or cauliflower-like lesions, most commonly on the lower limbs. * **Diagnosis:** KOH mount of "black dots" on the lesion surface or biopsy reveals the characteristic **Sclerotic bodies**. * **Treatment:** Itraconazole is the drug of choice; surgical excision or cryotherapy may be used for small lesions.

Q: San Joaquin Valley fever is caused by which organism?

Coccidioides immitis. **Explanation:** **Coccidioides immitis** is the causative agent of **Coccidioidomycosis**, also known as **San Joaquin Valley fever** (or simply Valley fever). This fungal infection is endemic to the arid regions of the Southwestern United States (specifically the San Joaquin Valley in California) and Northern Mexico. It is a dimorphic fungus that exists as mold in the soil and transforms into **spherules containing endospores** within the host lungs. **Analysis of Options:** * **B. dermatitidis (Blastomycosis):** Known as "North American Blastomycosis" or "Gilchrist’s disease." It is endemic to the Ohio and Mississippi River valleys and is characterized by "Broad-Based Budding" yeast. * **Cryptococcus neoformans:** An opportunistic encapsulated yeast (not dimorphic) commonly associated with pigeon droppings. It is a leading cause of fungal meningitis in HIV/AIDS patients. * **H. capsulatum (Histoplasmosis):** Known as "Darling’s disease" or "Ohio Valley Fever." It is associated with bird or bat droppings (guano) and is characterized by small intracellular yeasts within macrophages. **High-Yield Clinical Pearls for NEET-PG:** * **Morphology:** *Coccidioides* is unique among dimorphic fungi; it forms **spherules** in tissue, not yeast. * **Transmission:** Inhalation of **arthroconidia** (infectious spores) from disturbed soil or during dust storms. * **Clinical Presentation:** Ranges from a self-limiting flu-like illness to severe pneumonia. A classic triad includes fever, joint pain (Desert Rheumatism), and **Erythema Nodosum**. * **Diagnosis:** Identification of thick-walled spherules filled with endospores on KOH mount or biopsy. Culture on Sabouraud Dextrose Agar (SDA) shows highly infectious arthroconidia.

Q: Gram stained periorbital exudates in severe panophthalmitis with cellulitis in an elderly diabetic shows irregular branching aseptate and broad hyphae. Which of the following is the most likely diagnosis?

Apophysomyces species. ### Explanation **Correct Answer: D. Apophysomyces species** The clinical presentation of severe panophthalmitis and cellulitis in an elderly diabetic patient, combined with the specific microscopic findings, points directly to **Mucormycosis**. **Why Apophysomyces is correct:** * **Microscopic Morphology:** The description of **"irregular branching, aseptate (coenocytic), and broad hyphae"** is the classic hallmark of the order Mucorales. * **Clinical Context:** Diabetics are highly predisposed to Rhino-oculo-cerebral mucormycosis (ROCM). * **Genus Identification:** While *Rhizopus* is the most common cause globally, *Apophysomyces elegans* is a significant cause of invasive mucormycosis in India, often following trauma or in immunocompromised states. Among the given options, it is the only member of the Mucorales family. **Why other options are incorrect:** * **A. Candida:** Shows budding yeast cells and **pseudohyphae** (constrictions at septa), not broad aseptate hyphae. * **B. Aspergillus:** Characterized by **septate** hyphae with regular, **dichotomous branching at acute angles** (45°). * **C. Penicillium:** Also features septate hyphae and characteristic "brush-like" conidiophores (Penicillus) in culture; it does not match the "broad aseptate" description. **High-Yield Clinical Pearls for NEET-PG:** * **Staining:** Mucorales are best visualized with **KOH mount** or silver stains (GMS/PAS). They often stain weakly on Gram stain but appear as "ghost-like" broad outlines. * **Risk Factors:** Diabetic Ketoacidosis (DKA) is the classic association because Mucorales thrive in acidic, iron-rich environments (using siderophores). * **Treatment:** The drug of choice is **Liposomal Amphotericin B**, along with aggressive surgical debridement. * **Key Distinction:** * *Mucor/Rhizopus:* Aseptate, wide-angle (90°) branching. * *Aspergillus:* Septate, acute-angle (45°) branching.

Q: Maltese cross formation is observed on polarizing microscopy in which of the following?

Cryptococcus neoformans. **Explanation:** The correct answer is **Cryptococcus neoformans**. **Why it is correct:** *Cryptococcus neoformans* is an encapsulated yeast. When clinical specimens (such as CSF or tissue sections) or cultures are viewed under **polarizing microscopy**, the thick polysaccharide capsule exhibits **birefringence**. This optical property results in the characteristic **"Maltese cross"** appearance (a cross-shaped light pattern). This is a high-yield diagnostic feature used to identify the fungus in histopathological sections, especially when stained with Gomori Methenamine Silver (GMS) or PAS. **Analysis of Incorrect Options:** * **Penicillium marneffei (Talaromyces marneffei):** This is a dimorphic fungus characterized by intracellular yeast cells with a central transverse septum (fission). It does not show a Maltese cross. * **Plasmodium falciparum:** This is a protozoan parasite. While it produces hemozoin pigment, it does not exhibit the Maltese cross pattern. (Note: *Babesia* species show a "Maltese cross" arrangement of four merozoites in RBCs, but this is a structural arrangement, not a polarizing microscopy finding). * **Candida albicans:** This yeast typically shows budding cells and pseudohyphae. Its cell wall does not produce a birefringent Maltese cross under polarization. **NEET-PG High-Yield Pearls:** 1. **Maltese Cross in Microbiology:** Seen in *Cryptococcus* (polarizing microscopy) and *Babesia* (tetrad arrangement on Giemsa stain). 2. **Maltese Cross in Pathology:** Seen in **Urinary lipids** (nephrotic syndrome), **Starch granules** (contaminants), and **Ethyl glycol poisoning** (calcium oxalate crystals). 3. **Cryptococcus Stains:** India Ink (negative staining for capsule), Mucicarmine (bright red capsule), and Fontana-Masson (detects melanin in the cell wall). 4. **Virulence Factor:** The polysaccharide capsule (GXM) is the primary virulence factor, inhibiting phagocytosis.

Q: Cigar bodies are seen in which condition?

Sporotrichosis. **Explanation:** **Sporotrichosis** is a subcutaneous fungal infection caused by the dimorphic fungus *Sporothrix schenckii*. The correct answer is **A** because "Cigar bodies" are the characteristic tissue form of this fungus. * **Why it is correct:** In tissue biopsies (at 37°C), *Sporothrix schenckii* exists as pleomorphic, elongated, fusiform yeast cells measuring 1–3 µm by 3–10 µm. Their elongated shape resembles a cigar, hence the term **"Cigar bodies."** These are often difficult to visualize on routine H&E stains and are better seen with PAS or GMS stains. **Why other options are incorrect:** * **Chromoblastomycosis:** Characterized by **Medlar bodies** (Sclerotic bodies/Copper-penny bodies), which are thick-walled, dark brown, multiseptate fungal cells. * **Mycetoma:** Characterized by the presence of **grains** or granules (sulfur granules in actinomycetoma or fungal hyphae in eumycetoma) draining from sinuses. * **Basidiomycosis:** Typically presents as subcutaneous zygomycosis (e.g., *Conidiobolus*), characterized by thin-walled, sparsely septate hyphae often surrounded by an eosinophilic halo (**Splendore-Hoeppli phenomenon**). **High-Yield Clinical Pearls for NEET-PG:** * **Occupational Hazard:** Known as **"Rose Gardener’s Disease"** due to traumatic inoculation via thorns. * **Clinical Presentation:** Presents as a linear chain of nodules along the lymphatic drainage (**Sporotrichoid spread**). * **Asteroid Bodies:** In tissue, yeast cells may be surrounded by eosinophilic radiating processes (Splendore-Hoeppli phenomenon), termed Asteroid bodies. * **Culture:** At 25°C, it shows a "Flower-like" or **"Daisy petal"** arrangement of conidia. * **Treatment:** Drug of choice is **Itraconazole**. Historically, saturated solution of potassium iodide (SSKI) was used.

Q: Which dermatophyte species does not involve the nail?

Microsporum. ### Explanation The correct answer is **Microsporum**. The classification of dermatophytes into three genera—*Trichophyton*, *Microsporum*, and *Epidermophyton*—is based on the specific keratinized tissues they can invade (skin, hair, and nails). **1. Why Microsporum is correct:** *Microsporum* species primarily infect the **hair and skin**. They lack the biochemical capability to effectively invade the nail plate. Therefore, it is the only genus among the three that does not cause Onychomycosis (nail infection). **2. Why the other options are incorrect:** * **Trichophyton:** This is the most versatile genus. It can involve all three keratinized structures: **Skin, Hair, and Nails**. *T. rubrum* is the most common cause of Onychomycosis worldwide. * **Epidermophyton:** This genus involves the **Skin and Nails** but notably **does not involve the hair**. *Epidermophyton floccosum* is a common cause of Tinea cruris and Onychomycosis. **3. High-Yield Clinical Pearls for NEET-PG:** To quickly memorize the tissue involvement, use this simple table: | Genus | Skin | Hair | Nails | | :--- | :---: | :---: | :---: | | **Trichophyton** | Yes | Yes | Yes | | **Microsporum** | Yes | Yes | **No** | | **Epidermophyton** | Yes | **No** | Yes | * **Wood’s Lamp Examination:** *Microsporum* species (like *M. audouinii* and *M. canis*) typically show a brilliant greenish fluorescence, whereas most *Trichophyton* species (except *T. schoenleinii*) do not fluoresce. * **Macroconidia Shape:** *Microsporum* has spindle-shaped macroconidia, *Trichophyton* has pencil-shaped, and *Epidermophyton* has club-shaped macroconidia.

Q: A 31-year-old woman has had vulvar pruritus along with a thick, whitish, odorless, globular vaginal discharge for the past week. On pelvic examination, the cervix appears erythematous, but there are no erosions or masses. A Pap smear shows budding cells and pseudo hyphae. No dysplastic cells are present. Which of the following infectious agents is most likely to produce these findings?

Candida albicans. ### Explanation The clinical presentation and laboratory findings are classic for **Vulvovaginal Candidiasis (VVC)**, most commonly caused by *Candida albicans*. **Why the correct answer is right:** * **Clinical Features:** The "thick, whitish, odorless, globular" discharge is often described as **curd-like** or **cottage cheese-like**. Vulvar pruritus (itching) is the hallmark symptom. * **Microscopy:** The Pap smear (or a KOH mount) showing **budding yeast cells and pseudohyphae** is the definitive diagnostic feature for *Candida*. While Pap smears are for cytology, they frequently incidentally detect fungal elements. * **Physical Exam:** Erythema of the cervix and vaginal walls is common due to inflammation, but unlike other infections, the discharge remains odorless. **Why the incorrect options are wrong:** * **Chlamydia trachomatis:** Typically causes a mucopurulent cervicitis. It is an obligate intracellular bacterium and would not show pseudohyphae on microscopy. * **Neisseria gonorrhoeae:** Causes purulent cervical discharge and pelvic inflammatory disease. Diagnosis is via Gram stain (Gram-negative diplococci) or NAAT, not fungal elements. * **Trichomonas vaginalis:** Characterized by a **foul-smelling, greenish-yellow, frothy** discharge. On examination, one would expect a "strawberry cervix" (punctate hemorrhages) and motile flagellated organisms on a wet mount. **High-Yield Pearls for NEET-PG:** * **Risk Factors:** Pregnancy, Diabetes Mellitus, recent antibiotic use, and immunosuppression (HIV). * **pH Level:** In Candidiasis, the vaginal pH is typically **normal ( 4.5. * **Treatment:** First-line treatment is topical or oral azoles (e.g., **Fluconazole** 150mg single dose). Note: Oral fluconazole is contraindicated in pregnancy; use topical clotrimazole instead.

Question 1

Which statement is false regarding Cryptococcus neoformans?

Accepted Answer

Urease negative

Answer

Grows at 5°C and 37°C

Answer

Has 4 serotypes

Answer

Causes superficial skin infection

Question 2

About 90 days post-bone marrow transplant, a 55-year-old white woman began to complain of dry cough, shortness of breath, and chest pain. She was started on antibiotics and blood culture obtained at the time was negative and there was not improvement. A computed tomography (CT) scan of the lungs showed a halo of low attenuation around a nodular lesion. Analysis of lung biopsy was similar to methenamine silver-stained section below. What is the most likely diagnosis for this patient?

Accepted Answer

Aspergillosis

Answer

Candidiasis

Answer

Histoplasmosis

Answer

Mucormycosis

Question 3

Brown, spherical, septate bodies found in pus are diagnostic of which condition?

Accepted Answer

Chromomycosis

Answer

Geotrichosis

Answer

Mucormycosis

Answer

Sporotrichosis

Question 4

San Joaquin Valley fever is caused by which organism?

Accepted Answer

Coccidioides immitis

Answer

B. dermatitidis

Answer

Cryptococcus neoformans

Answer

H. capsulatum

Question 5

Opportunistic lung infections in AIDS are most commonly caused by which of the following pathogens?

Accepted Answer

Pneumocystis jirovecii

Answer

Klebsiella pneumoniae

Answer

Mucor species

Answer

Mycoplasma pneumoniae

Question 6

Gram stained periorbital exudates in severe panophthalmitis with cellulitis in an elderly diabetic shows irregular branching aseptate and broad hyphae. Which of the following is the most likely diagnosis?

Accepted Answer

Apophysomyces species

Answer

Candida

Answer

Aspergillus

Answer

Pencillium

Question 7

Maltese cross formation is observed on polarizing microscopy in which of the following?

Accepted Answer

Cryptococcus neoformans

Answer

Penicillium marneffei

Answer

Plasmodium falciparum

Answer

Candida albicans

Question 8

Cigar bodies are seen in which condition?

Accepted Answer

Sporotrichosis

Answer

Chromoblastomycosis

Answer

Mycetoma

Answer

Basidiomycosis

Question 9

Which dermatophyte species does not involve the nail?

Accepted Answer

Microsporum

Answer

Trichophyton

Answer

Epidermophyton

Answer

None of the above

Question 10

A 31-year-old woman has had vulvar pruritus along with a thick, whitish, odorless, globular vaginal discharge for the past week. On pelvic examination, the cervix appears erythematous, but there are no erosions or masses. A Pap smear shows budding cells and pseudo hyphae. No dysplastic cells are present. Which of the following infectious agents is most likely to produce these findings?

Accepted Answer

Candida albicans

Answer

Chlamydia trachomatis

Answer

Neisseria gonorrhoeae

Answer

Trichomonas vaginalis

Mycology — MCQs

Mycology — MCQs

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